How to Make a Custom Page with no Header Image in Theme Twenty-Twelve

For this kind of job, I’d just hide it using CSS specific to that page only.

For example, this will hide header image and sidebar for the page id 226, and all its child pages.

.page-id-266 .header-image,
.parent-pageid-266 .header-image,
.page-id-266 #secondary,
.parent-pageid-266 #secondary {
      display: none;
}
.page-id-266 .site-content,
.parent-pageid-266 .site-content {
     float: none;
     width: 100%;
}

Since you already on a child theme, use that code at the bottom of your child theme’s style.css.

Paul, thank you very much ! … I will test it this morning, and I am sure it will work perfectly.

Hi Paul and everyone. I tried to add the code to the style sheet page, but it seems to have no effect on the way the page looks — the page still has a header and sidebar. I am pasting the code here below, the code for the style sheet, with new css added at the very end of the file. Thanks again for your help !
==============================================
/*
Theme Name: Twenty Twelve
Theme URI: https://www.ads-software.com/themes/twentytwelve/
Author: the WordPress team
Author URI: https://www.ads-software.com/
Description: The 2012 theme for WordPress is a fully responsive theme that looks great on any device. Features include a front page template with its own widgets, an optional display font, styling for post formats on both index and single views, and an optional no-sidebar page template. Make it yours with a custom menu, header image, and background.
Version: 2.1
License: GNU General Public License v2 or later
License URI: https://www.gnu.org/licenses/gpl-2.0.html
Tags: blog, one-column, two-columns, right-sidebar, custom-background, custom-header, custom-menu, editor-style, featured-images, flexible-header, footer-widgets, full-width-template, microformats, post-formats, rtl-language-support, sticky-post, theme-options, translation-ready
Text Domain: twentytwelve

This theme, like WordPress, is licensed under the GPL.
Use it to make something cool, have fun, and share what you’ve learned with others.
*/

/* =Notes
————————————————————–
This stylesheet uses rem values with a pixel fallback. The rem
values (and line heights) are calculated using two variables:

$rembase: 14;
$line-height: 24;

———- Examples

* Use a pixel value with a rem fallback for font-size, padding, margins, etc.
padding: 5px 0;
padding: 0.357142857rem 0; (5 / $rembase)

* Set a font-size and then set a line-height based on the font-size
font-size: 16px
font-size: 1.142857143rem; (16 / $rembase)
line-height: 1.5; ($line-height / 16)

———- Vertical spacing

Vertical spacing between most elements should use 24px or 48px
to maintain vertical rhythm:

.my-new-div {
margin: 24px 0;
margin: 1.714285714rem 0; ( 24 / $rembase )
}

———- Further reading

https://snook.ca/archives/html_and_css/font-size-with-rem
https://blog.typekit.com/2011/11/09/type-study-sizing-the-legible-letter/

/* =Reset
————————————————————– */

html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, dl, dt, dd, ol, ul, li, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td, article, aside, canvas, details, embed, figure, figcaption, footer, header, hgroup, menu, nav, output, ruby, section, summary, time, mark, audio, video {
margin: 0;
padding: 0;
border: 0;
font-size: 100%;
vertical-align: baseline;
}
body {
line-height: 1;
}
ol,
ul {
list-style: none;
}
blockquote,
q {
quotes: none;
}
blockquote:before,
blockquote:after,
q:before,
q:after {
content: ”;
content: none;
}
table {
border-collapse: collapse;
border-spacing: 0;
}
caption,
th,
td {
font-weight: normal;
text-align: left;
}
h1,
h2,
h3,
h4,
h5,
h6 {
clear: both;
}
html {
overflow-y: scroll;
font-size: 100%;
-webkit-text-size-adjust: 100%;
-ms-text-size-adjust: 100%;
}
a:focus {
outline: thin dotted;
}
article,
aside,
details,
figcaption,
figure,
footer,
header,
hgroup,
nav,
section {
display: block;
}
audio,
canvas,
video {
display: inline-block;
}
audio:not([controls]) {
display: none;
}
del {
color: #333;
}
ins {
background: #fff9c0;
text-decoration: none;
}
hr {
background-color: #ccc;
border: 0;
height: 1px;
margin: 24px;
margin-bottom: 1.714285714rem;
}
sub,
sup {
font-size: 75%;
line-height: 0;
position: relative;
vertical-align: baseline;
}
sup {
top: -0.5em;
}
sub {
bottom: -0.25em;
}
small {
font-size: smaller;
}
img {
border: 0;
-ms-interpolation-mode: bicubic;
}

/* Clearing floats */
.clear:after,
.wrapper:after,
.format-status .entry-header:after {
clear: both;
}
.clear:before,
.clear:after,
.wrapper:before,
.wrapper:after,
.format-status .entry-header:before,
.format-status .entry-header:after {
display: table;
content: “”;
}

/* =Repeatable patterns
————————————————————– */

/* Small headers */
.archive-title,
.page-title,
.widget-title,
.entry-content th,
.comment-content th {
font-size: 11px;
font-size: 0.785714286rem;
line-height: 2.181818182;
font-weight: bold;
text-transform: uppercase;
color: #636363;
}

/* Shared Post Format styling */
article.format-quote footer.entry-meta,
article.format-link footer.entry-meta,
article.format-status footer.entry-meta {
font-size: 11px;
font-size: 0.785714286rem;
line-height: 2.181818182;
}

/* Form fields, general styles first */
button,
input,
select,
textarea {
border: 1px solid #ccc;
border-radius: 3px;
font-family: inherit;
padding: 6px;
padding: 0.428571429rem;
}
button,
input {
line-height: normal;
}
textarea {
font-size: 100%;
overflow: auto;
vertical-align: top;
}

/* Reset non-text input types */
input[type=”checkbox”],
input[type=”radio”],
input[type=”file”],
input[type=”hidden”],
input[type=”image”],
input[type=”color”] {
border: 0;
border-radius: 0;
padding: 0;
}

/* Buttons */
.menu-toggle,
input[type=”submit”],
input[type=”button”],
input[type=”reset”],
article.post-password-required input[type=submit],
.bypostauthor cite span {
padding: 6px 10px;
padding: 0.428571429rem 0.714285714rem;
font-size: 11px;
font-size: 0.785714286rem;
line-height: 1.428571429;
font-weight: normal;
color: #7c7c7c;
background-color: #e6e6e6;
background-repeat: repeat-x;
background-image: -moz-linear-gradient(top, #f4f4f4, #e6e6e6);
background-image: -ms-linear-gradient(top, #f4f4f4, #e6e6e6);
background-image: -webkit-linear-gradient(top, #f4f4f4, #e6e6e6);
background-image: -o-linear-gradient(top, #f4f4f4, #e6e6e6);
background-image: linear-gradient(top, #f4f4f4, #e6e6e6);
border: 1px solid #d2d2d2;
border-radius: 3px;
box-shadow: 0 1px 2px rgba(64, 64, 64, 0.1);
}
.menu-toggle,
button,
input[type=”submit”],
input[type=”button”],
input[type=”reset”] {
cursor: pointer;
}
button[disabled],
input[disabled] {
cursor: default;
}
.menu-toggle:hover,
.menu-toggle:focus,
button:hover,
input[type=”submit”]:hover,
input[type=”button”]:hover,
input[type=”reset”]:hover,
article.post-password-required input[type=submit]:hover {
color: #5e5e5e;
background-color: #ebebeb;
background-repeat: repeat-x;
background-image: -moz-linear-gradient(top, #f9f9f9, #ebebeb);
background-image: -ms-linear-gradient(top, #f9f9f9, #ebebeb);
background-image: -webkit-linear-gradient(top, #f9f9f9, #ebebeb);
background-image: -o-linear-gradient(top, #f9f9f9, #ebebeb);
background-image: linear-gradient(top, #f9f9f9, #ebebeb);
}
.menu-toggle:active,
.menu-toggle.toggled-on,
button:active,
input[type=”submit”]:active,
input[type=”button”]:active,
input[type=”reset”]:active {
color: #757575;
background-color: #e1e1e1;
background-repeat: repeat-x;
background-image: -moz-linear-gradient(top, #ebebeb, #e1e1e1);
background-image: -ms-linear-gradient(top, #ebebeb, #e1e1e1);
background-image: -webkit-linear-gradient(top, #ebebeb, #e1e1e1);
background-image: -o-linear-gradient(top, #ebebeb, #e1e1e1);
background-image: linear-gradient(top, #ebebeb, #e1e1e1);
box-shadow: inset 0 0 8px 2px #c6c6c6, 0 1px 0 0 #f4f4f4;
border-color: transparent;
}
.bypostauthor cite span {
color: #fff;
background-color: #21759b;
background-image: none;
border: 1px solid #1f6f93;
border-radius: 2px;
box-shadow: none;
padding: 0;
}

/* Responsive images */
.entry-content img,
.comment-content img,
.widget img {
max-width: 100%; /* Fluid images for posts, comments, and widgets */
}
img[class*=”align”],
img[class*=”wp-image-“],
img[class*=”attachment-“] {
height: auto; /* Make sure images with WordPress-added height and width attributes are scaled correctly */
}
img.size-full,
img.size-large,
img.header-image,
img.wp-post-image {
max-width: 100%;
height: auto; /* Make sure images with WordPress-added height and width attributes are scaled correctly */
}

/* Make sure videos and embeds fit their containers */
embed,
iframe,
object,
video {
max-width: 100%;
}
.entry-content .twitter-tweet-rendered {
max-width: 100% !important; /* Override the Twitter embed fixed width */
}

/* Images */
.alignleft {
float: left;
}
.alignright {
float: right;
}
.aligncenter {
display: block;
margin-left: auto;
margin-right: auto;
}
.entry-content img,
.comment-content img,
.widget img,
img.header-image,
.author-avatar img,
img.wp-post-image {
/* Add fancy borders to all WordPress-added images but not things like badges and icons and the like */
border-radius: 3px;
box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2);
}
.wp-caption {
max-width: 100%; /* Keep wide captions from overflowing their container. */
padding: 4px;
}
.wp-caption .wp-caption-text,
.gallery-caption,
.entry-caption {
font-style: italic;
font-size: 12px;
font-size: 0.857142857rem;
line-height: 2;
color: #757575;
}
img.wp-smiley,
.rsswidget img {
border: 0;
border-radius: 0;
box-shadow: none;
margin-bottom: 0;
margin-top: 0;
padding: 0;
}
.entry-content dl.gallery-item {
margin: 0;
}
.gallery-item a,
.gallery-caption {
width: 90%;
}
.gallery-item a {
display: block;
}
.gallery-caption a {
display: inline;
}
.gallery-columns-1 .gallery-item a {
max-width: 100%;
width: auto;
}
.gallery .gallery-icon img {
height: auto;
max-width: 90%;
padding: 5%;
}
.gallery-columns-1 .gallery-icon img {
padding: 3%;
}

/* Navigation */
.site-content nav {
clear: both;
line-height: 2;
overflow: hidden;
}
#nav-above {
padding: 24px 0;
padding: 1.714285714rem 0;
}
#nav-above {
display: none;
}
.paged #nav-above {
display: block;
}
.nav-previous,
.previous-image {
float: left;
width: 50%;
}
.nav-next,
.next-image {
float: right;
text-align: right;
width: 50%;
}
.nav-single + .comments-area,
#comment-nav-above {
margin: 48px 0;
margin: 3.428571429rem 0;
}

/* Author profiles */
.author .archive-header {
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
.author-info {
border-top: 1px solid #ededed;
margin: 24px 0;
margin: 1.714285714rem 0;
padding-top: 24px;
padding-top: 1.714285714rem;
overflow: hidden;
}
.author-description p {
color: #757575;
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
}
.author.archive .author-info {
border-top: 0;
margin: 0 0 48px;
margin: 0 0 3.428571429rem;
}
.author.archive .author-avatar {
margin-top: 0;
}

/* =Basic structure
————————————————————– */

/* Body, links, basics */
html {
font-size: 87.5%;
}
body {
font-size: 14px;
font-size: 1rem;
font-family: Helvetica, Arial, sans-serif;
text-rendering: optimizeLegibility;
color: #444;
}
body.custom-font-enabled {
font-family: “Open Sans”, Helvetica, Arial, sans-serif;
}
a {
outline: none;
color: #21759b;
}
a:hover {
color: #0f3647;
}

/* Assistive text */
.assistive-text,
.site .screen-reader-text {
position: absolute !important;
clip: rect(1px, 1px, 1px, 1px);
overflow: hidden;
height: 1px;
width: 1px;
}
.main-navigation .assistive-text:focus,
.site .screen-reader-text:hover,
.site .screen-reader-text:active,
.site .screen-reader-text:focus {
background: #fff;
border: 2px solid #333;
border-radius: 3px;
clip: auto !important;
color: #000;
display: block;
font-size: 12px;
height: auto;
padding: 12px;
position: absolute;
top: 5px;
left: 5px;
width: auto;
z-index: 100000; /* Above WP toolbar */
}

/* Page structure */
.site {
padding: 0 24px;
padding: 0 1.714285714rem;
background-color: #fff;
}
.site-content {
margin: 24px 0 0;
margin: 1.714285714rem 0 0;
}
.widget-area {
margin: 24px 0 0;
margin: 1.714285714rem 0 0;
}

/* Header */
.site-header {
padding: 24px 0;
padding: 1.714285714rem 0;
}
.site-header h1,
.site-header h2 {
text-align: center;
}
.site-header h1 a,
.site-header h2 a {
color: #515151;
display: inline-block;
text-decoration: none;
}
.site-header h1 a:hover,
.site-header h2 a:hover {
color: #21759b;
}
.site-header h1 {
font-size: 24px;
font-size: 1.714285714rem;
line-height: 1.285714286;
margin-bottom: 14px;
margin-bottom: 1rem;
}
.site-header h2 {
font-weight: normal;
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
color: #757575;
}
.header-image {
margin-top: 24px;
margin-top: 1.714285714rem;
}

/* Navigation Menu */
.main-navigation {
margin-top: 24px;
margin-top: 1.714285714rem;
text-align: center;
}
.main-navigation li {
margin-top: 24px;
margin-top: 1.714285714rem;
font-size: 12px;
font-size: 0.857142857rem;
line-height: 1.42857143;
}
.main-navigation a {
color: #5e5e5e;
}
.main-navigation a:hover,
.main-navigation a:focus {
color: #21759b;
}
.main-navigation ul.nav-menu,
.main-navigation div.nav-menu > ul {
display: none;
}
.main-navigation ul.nav-menu.toggled-on,
.menu-toggle {
display: inline-block;
}

/* Banner */
section[role=”banner”] {
margin-bottom: 48px;
margin-bottom: 3.428571429rem;
}

/* Sidebar */
.widget-area .widget {
-webkit-hyphens: auto;
-moz-hyphens: auto;
hyphens: auto;
margin-bottom: 48px;
margin-bottom: 3.428571429rem;
word-wrap: break-word;
}
.widget-area .widget h3 {
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
.widget-area .widget p,
.widget-area .widget li,
.widget-area .widget .textwidget {
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
}
.widget-area .widget p {
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
.widget-area .textwidget ul {
list-style: disc outside;
margin: 0 0 24px;
margin: 0 0 1.714285714rem;
}
.widget-area .textwidget li {
margin-left: 36px;
margin-left: 2.571428571rem;
}
.widget-area .widget a {
color: #757575;
}
.widget-area .widget a:hover {
color: #21759b;
}
.widget-area .widget a:visited {
color: #9f9f9f;
}
.widget-area #s {
width: 53.66666666666%; /* define a width to avoid dropping a wider submit button */
}

/* Footer */
footer[role=”contentinfo”] {
border-top: 1px solid #ededed;
clear: both;
font-size: 12px;
font-size: 0.857142857rem;
line-height: 2;
max-width: 960px;
max-width: 68.571428571rem;
margin-top: 24px;
margin-top: 1.714285714rem;
margin-left: auto;
margin-right: auto;
padding: 24px 0;
padding: 1.714285714rem 0;
}
footer[role=”contentinfo”] a {
color: #686868;
}
footer[role=”contentinfo”] a:hover {
color: #21759b;
}

/* =Main content and comment content
————————————————————– */

.entry-meta {
clear: both;
}
.entry-header {
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
.entry-header img.wp-post-image {
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
.entry-header .entry-title {
font-size: 20px;
font-size: 1.428571429rem;
line-height: 1.2;
font-weight: normal;
}
.entry-header .entry-title a {
text-decoration: none;
}
.entry-header .entry-format {
margin-top: 24px;
margin-top: 1.714285714rem;
font-weight: normal;
}
.entry-header .comments-link {
margin-top: 24px;
margin-top: 1.714285714rem;
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
color: #757575;
}
.comments-link a,
.entry-meta a {
color: #757575;
}
.comments-link a:hover,
.entry-meta a:hover {
color: #21759b;
}
article.sticky .featured-post {
border-top: 4px double #ededed;
border-bottom: 4px double #ededed;
color: #757575;
font-size: 13px;
font-size: 0.928571429rem;
line-height: 3.692307692;
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
text-align: center;
}
.entry-content,
.entry-summary,
.mu_register {
line-height: 1.714285714;
}
.entry-content h1,
.comment-content h1,
.entry-content h2,
.comment-content h2,
.entry-content h3,
.comment-content h3,
.entry-content h4,
.comment-content h4,
.entry-content h5,
.comment-content h5,
.entry-content h6,
.comment-content h6 {
margin: 24px 0;
margin: 1.714285714rem 0;
line-height: 1.714285714;
}
.entry-content h1,
.comment-content h1 {
font-size: 21px;
font-size: 1.5rem;
line-height: 1.5;
}
.entry-content h2,
.comment-content h2,
.mu_register h2 {
font-size: 18px;
font-size: 1.285714286rem;
line-height: 1.6;
}
.entry-content h3,
.comment-content h3 {
font-size: 16px;
font-size: 1.142857143rem;
line-height: 1.846153846;
}
.entry-content h4,
.comment-content h4 {
font-size: 14px;
font-size: 1rem;
line-height: 1.846153846;
}
.entry-content h5,
.comment-content h5 {
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
}
.entry-content h6,
.comment-content h6 {
font-size: 12px;
font-size: 0.857142857rem;
line-height: 1.846153846;
}
.entry-content p,
.entry-summary p,
.comment-content p,
.mu_register p {
margin: 0 0 24px;
margin: 0 0 1.714285714rem;
line-height: 1.714285714;
}
.entry-content a:visited,
.comment-content a:visited {
color: #9f9f9f;
}
.entry-content .more-link {
white-space: nowrap;
}
.entry-content ol,
.comment-content ol,
.entry-content ul,
.comment-content ul,
.mu_register ul {
margin: 0 0 24px;
margin: 0 0 1.714285714rem;
line-height: 1.714285714;
}
.entry-content ul ul,
.comment-content ul ul,
.entry-content ol ol,
.comment-content ol ol,
.entry-content ul ol,
.comment-content ul ol,
.entry-content ol ul,
.comment-content ol ul {
margin-bottom: 0;
}
.entry-content ul,
.comment-content ul,
.mu_register ul {
list-style: disc outside;
}
.entry-content ol,
.comment-content ol {
list-style: decimal outside;
}
.entry-content li,
.comment-content li,
.mu_register li {
margin: 0 0 0 36px;
margin: 0 0 0 2.571428571rem;
}
.entry-content blockquote,
.comment-content blockquote {
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
padding: 24px;
padding: 1.714285714rem;
font-style: italic;
}
.entry-content blockquote p:last-child,
.comment-content blockquote p:last-child {
margin-bottom: 0;
}
.entry-content code,
.comment-content code {
font-family: Consolas, Monaco, Lucida Console, monospace;
font-size: 12px;
font-size: 0.857142857rem;
line-height: 2;
}
.entry-content pre,
.comment-content pre {
border: 1px solid #ededed;
color: #666;
font-family: Consolas, Monaco, Lucida Console, monospace;
font-size: 12px;
font-size: 0.857142857rem;
line-height: 1.714285714;
margin: 24px 0;
margin: 1.714285714rem 0;
overflow: auto;
padding: 24px;
padding: 1.714285714rem;
}
.entry-content pre code,
.comment-content pre code {
display: block;
}
.entry-content abbr,
.comment-content abbr,
.entry-content dfn,
.comment-content dfn,
.entry-content acronym,
.comment-content acronym {
border-bottom: 1px dotted #666;
cursor: help;
}
.entry-content address,
.comment-content address {
display: block;
line-height: 1.714285714;
margin: 0 0 24px;
margin: 0 0 1.714285714rem;
}
img.alignleft,
.wp-caption.alignleft {
margin: 12px 24px 12px 0;
margin: 0.857142857rem 1.714285714rem 0.857142857rem 0;
}
img.alignright,
.wp-caption.alignright {
margin: 12px 0 12px 24px;
margin: 0.857142857rem 0 0.857142857rem 1.714285714rem;
}
img.aligncenter,
.wp-caption.aligncenter {
clear: both;
margin-top: 12px;
margin-top: 0.857142857rem;
margin-bottom: 12px;
margin-bottom: 0.857142857rem;
}
.entry-content embed,
.entry-content iframe,
.entry-content object,
.entry-content video {
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
.entry-content dl,
.comment-content dl {
margin: 0 24px;
margin: 0 1.714285714rem;
}
.entry-content dt,
.comment-content dt {
font-weight: bold;
line-height: 1.714285714;
}
.entry-content dd,
.comment-content dd {
line-height: 1.714285714;
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
.entry-content table,
.comment-content table {
border-bottom: 1px solid #ededed;
color: #757575;
font-size: 12px;
font-size: 0.857142857rem;
line-height: 2;
margin: 0 0 24px;
margin: 0 0 1.714285714rem;
width: 100%;
}
.entry-content table caption,
.comment-content table caption {
font-size: 16px;
font-size: 1.142857143rem;
margin: 24px 0;
margin: 1.714285714rem 0;
}
.entry-content td,
.comment-content td {
border-top: 1px solid #ededed;
padding: 6px 10px 6px 0;
}
.site-content article {
border-bottom: 4px double #ededed;
margin-bottom: 72px;
margin-bottom: 5.142857143rem;
padding-bottom: 24px;
padding-bottom: 1.714285714rem;
word-wrap: break-word;
-webkit-hyphens: auto;
-moz-hyphens: auto;
hyphens: auto;
}
.page-links {
clear: both;
line-height: 1.714285714;
}
footer.entry-meta {
margin-top: 24px;
margin-top: 1.714285714rem;
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
color: #757575;
}
.single-author .entry-meta .by-author {
display: none;
}
.mu_register h2 {
color: #757575;
font-weight: normal;
}

/* =Archives
————————————————————– */

.archive-header,
.page-header {
margin-bottom: 48px;
margin-bottom: 3.428571429rem;
padding-bottom: 22px;
padding-bottom: 1.571428571rem;
border-bottom: 1px solid #ededed;
}
.archive-meta {
color: #757575;
font-size: 12px;
font-size: 0.857142857rem;
line-height: 2;
margin-top: 22px;
margin-top: 1.571428571rem;
}

/* =Single audio/video attachment view
————————————————————– */

.attachment .entry-content .mejs-audio {
max-width: 400px;
}

.attachment .entry-content .mejs-container {
margin-bottom: 24px;
}

/* =Single image attachment view
————————————————————– */

.article.attachment {
overflow: hidden;
}
.image-attachment div.attachment {
text-align: center;
}
.image-attachment div.attachment p {
text-align: center;
}
.image-attachment div.attachment img {
display: block;
height: auto;
margin: 0 auto;
max-width: 100%;
}
.image-attachment .entry-caption {
margin-top: 8px;
margin-top: 0.571428571rem;
}

/* =Aside post format
————————————————————– */

article.format-aside h1 {
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
article.format-aside h1 a {
text-decoration: none;
color: #4d525a;
}
article.format-aside h1 a:hover {
color: #2e3542;
}
article.format-aside .aside {
padding: 24px 24px 0;
padding: 1.714285714rem;
background: #d2e0f9;
border-left: 22px solid #a8bfe8;
}
article.format-aside p {
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
color: #4a5466;
}
article.format-aside blockquote:last-child,
article.format-aside p:last-child {
margin-bottom: 0;
}

/* =Post formats
————————————————————– */

/* Image posts */
article.format-image footer h1 {
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
font-weight: normal;
}
article.format-image footer h2 {
font-size: 11px;
font-size: 0.785714286rem;
line-height: 2.181818182;
}
article.format-image footer a h2 {
font-weight: normal;
}

/* Link posts */
article.format-link header {
padding: 0 10px;
padding: 0 0.714285714rem;
float: right;
font-size: 11px;
font-size: 0.785714286rem;
line-height: 2.181818182;
font-weight: bold;
font-style: italic;
text-transform: uppercase;
color: #848484;
background-color: #ebebeb;
border-radius: 3px;
}
article.format-link .entry-content {
max-width: 80%;
float: left;
}
article.format-link .entry-content a {
font-size: 22px;
font-size: 1.571428571rem;
line-height: 1.090909091;
text-decoration: none;
}

/* Quote posts */
article.format-quote .entry-content p {
margin: 0;
padding-bottom: 24px;
padding-bottom: 1.714285714rem;
}
article.format-quote .entry-content blockquote {
display: block;
padding: 24px 24px 0;
padding: 1.714285714rem 1.714285714rem 0;
font-size: 15px;
font-size: 1.071428571rem;
line-height: 1.6;
font-style: normal;
color: #6a6a6a;
background: #efefef;
}

/* Status posts */
.format-status .entry-header {
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
.format-status .entry-header header {
display: inline-block;
}
.format-status .entry-header h1 {
font-size: 15px;
font-size: 1.071428571rem;
font-weight: normal;
line-height: 1.6;
margin: 0;
}
.format-status .entry-header h2 {
font-size: 12px;
font-size: 0.857142857rem;
font-weight: normal;
line-height: 2;
margin: 0;
}
.format-status .entry-header header a {
color: #757575;
}
.format-status .entry-header header a:hover {
color: #21759b;
}
.format-status .entry-header img {
float: left;
margin-right: 21px;
margin-right: 1.5rem;
}

/* =Comments
————————————————————– */

.comments-title {
margin-bottom: 48px;
margin-bottom: 3.428571429rem;
font-size: 16px;
font-size: 1.142857143rem;
line-height: 1.5;
font-weight: normal;
}
.comments-area article {
margin: 24px 0;
margin: 1.714285714rem 0;
}
.comments-area article header {
margin: 0 0 48px;
margin: 0 0 3.428571429rem;
overflow: hidden;
position: relative;
}
.comments-area article header img {
float: left;
padding: 0;
line-height: 0;
}
.comments-area article header cite,
.comments-area article header time {
display: block;
margin-left: 85px;
margin-left: 6.071428571rem;
}
.comments-area article header cite {
font-style: normal;
font-size: 15px;
font-size: 1.071428571rem;
line-height: 1.42857143;
}
.comments-area cite b {
font-weight: normal;
}
.comments-area article header time {
line-height: 1.714285714;
text-decoration: none;
font-size: 12px;
font-size: 0.857142857rem;
color: #5e5e5e;
}
.comments-area article header a {
text-decoration: none;
color: #5e5e5e;
}
.comments-area article header a:hover {
color: #21759b;
}
.comments-area article header cite a {
color: #444;
}
.comments-area article header cite a:hover {
text-decoration: underline;
}
.comments-area article header h4 {
position: absolute;
top: 0;
right: 0;
padding: 6px 12px;
padding: 0.428571429rem 0.857142857rem;
font-size: 12px;
font-size: 0.857142857rem;
font-weight: normal;
color: #fff;
background-color: #0088d0;
background-repeat: repeat-x;
background-image: -moz-linear-gradient(top, #009cee, #0088d0);
background-image: -ms-linear-gradient(top, #009cee, #0088d0);
background-image: -webkit-linear-gradient(top, #009cee, #0088d0);
background-image: -o-linear-gradient(top, #009cee, #0088d0);
background-image: linear-gradient(top, #009cee, #0088d0);
border-radius: 3px;
border: 1px solid #007cbd;
}
.comments-area .bypostauthor cite span {
position: absolute;
margin-left: 5px;
margin-left: 0.357142857rem;
padding: 2px 5px;
padding: 0.142857143rem 0.357142857rem;
font-size: 10px;
font-size: 0.714285714rem;
}
.comments-area .bypostauthor cite b {
font-weight: bold;
}
a.comment-reply-link,
a.comment-edit-link {
color: #686868;
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
}
a.comment-reply-link:hover,
a.comment-edit-link:hover {
color: #21759b;
}
.commentlist .pingback {
line-height: 1.714285714;
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}

/* Comment form */
#respond {
margin-top: 48px;
margin-top: 3.428571429rem;
}
#respond h3#reply-title {
font-size: 16px;
font-size: 1.142857143rem;
line-height: 1.5;
}
#respond h3#reply-title #cancel-comment-reply-link {
margin-left: 10px;
margin-left: 0.714285714rem;
font-weight: normal;
font-size: 12px;
font-size: 0.857142857rem;
}
#respond form {
margin: 24px 0;
margin: 1.714285714rem 0;
}
#respond form p {
margin: 11px 0;
margin: 0.785714286rem 0;
}
#respond form p.logged-in-as {
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
#respond form label {
display: block;
line-height: 1.714285714;
}
#respond form input[type=”text”],
#respond form textarea {
-moz-box-sizing: border-box;
box-sizing: border-box;
font-size: 12px;
font-size: 0.857142857rem;
line-height: 1.714285714;
padding: 10px;
padding: 0.714285714rem;
width: 100%;
}
#respond form p.form-allowed-tags {
margin: 0;
font-size: 12px;
font-size: 0.857142857rem;
line-height: 2;
color: #5e5e5e;
}
.required {
color: red;
}

/* =Front page template
————————————————————– */

.entry-page-image {
margin-bottom: 14px;
margin-bottom: 1rem;
}
.template-front-page .site-content article {
border: 0;
margin-bottom: 0;
}
.template-front-page .widget-area {
clear: both;
float: none;
width: auto;
padding-top: 24px;
padding-top: 1.714285714rem;
border-top: 1px solid #ededed;
}
.template-front-page .widget-area .widget li {
margin: 8px 0 0;
margin: 0.571428571rem 0 0;
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.714285714;
list-style-type: square;
list-style-position: inside;
}
.template-front-page .widget-area .widget li a {
color: #757575;
}
.template-front-page .widget-area .widget li a:hover {
color: #21759b;
}
.template-front-page .widget-area .widget_text img {
float: left;
margin: 8px 24px 8px 0;
margin: 0.571428571rem 1.714285714rem 0.571428571rem 0;
}

/* =Widgets
————————————————————– */

.widget-area .widget ul ul {
margin-left: 12px;
margin-left: 0.857142857rem;
}
.widget_rss li {
margin: 12px 0;
margin: 0.857142857rem 0;
}
.widget_recent_entries .post-date,
.widget_rss .rss-date {
color: #aaa;
font-size: 11px;
font-size: 0.785714286rem;
margin-left: 12px;
margin-left: 0.857142857rem;
}
#wp-calendar {
margin: 0;
width: 100%;
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
color: #686868;
}
#wp-calendar th,
#wp-calendar td,
#wp-calendar caption {
text-align: left;
}
#wp-calendar #next {
padding-right: 24px;
padding-right: 1.714285714rem;
text-align: right;
}
.widget_search label {
display: block;
font-size: 13px;
font-size: 0.928571429rem;
line-height: 1.846153846;
}
.widget_twitter li {
list-style-type: none;
}
.widget_twitter .timesince {
display: block;
text-align: right;
}

/* =Plugins
———————————————– */

img#wpstats {
display: block;
margin: 0 auto 24px;
margin: 0 auto 1.714285714rem;
}

/* =Media queries
————————————————————– */

/* Does the same thing as <meta name=”viewport” content=”width=device-width”>,
* but in the future W3C standard way. -ms- prefix is required for IE10+ to
* render responsive styling in Windows 8 “snapped” views; IE10+ does not honor
* the meta tag. See https://core.trac.www.ads-software.com/ticket/25888.
*/
@-ms-viewport {
width: device-width;
}
@viewport {
width: device-width;
}

/* Minimum width of 600 pixels. */
@media screen and (min-width: 600px) {
.author-avatar {
float: left;
margin-top: 8px;
margin-top: 0.571428571rem;
}
.author-description {
float: right;
width: 80%;
}
.site {
margin: 0 auto;
max-width: 960px;
max-width: 68.571428571rem;
overflow: hidden;
}
.site-content {
float: left;
width: 65.104166667%;
}
body.template-front-page .site-content,
body.attachment .site-content,
body.full-width .site-content {
width: 100%;
}
.widget-area {
float: right;
width: 26.041666667%;
}
.site-header h1,
.site-header h2 {
text-align: left;
}
.site-header h1 {
font-size: 26px;
font-size: 1.857142857rem;
line-height: 1.846153846;
margin-bottom: 0;
}
.main-navigation ul.nav-menu,
.main-navigation div.nav-menu > ul {
border-bottom: 1px solid #ededed;
border-top: 1px solid #ededed;
display: inline-block !important;
text-align: left;
width: 100%;
}
.main-navigation ul {
margin: 0;
text-indent: 0;
}
.main-navigation li a,
.main-navigation li {
display: inline-block;
text-decoration: none;
}
.main-navigation li a {
border-bottom: 0;
color: #6a6a6a;
line-height: 3.692307692;
text-transform: uppercase;
white-space: nowrap;
}
.main-navigation li a:hover,
.main-navigation li a:focus {
color: #000;
}
.main-navigation li {
margin: 0 40px 0 0;
margin: 0 2.857142857rem 0 0;
position: relative;
}
.main-navigation li ul {
margin: 0;
padding: 0;
position: absolute;
top: 100%;
z-index: 1;
height: 1px;
width: 1px;
overflow: hidden;
clip: rect(1px, 1px, 1px, 1px);
}
.main-navigation li ul ul {
top: 0;
left: 100%;
}
.main-navigation ul li:hover > ul,
.main-navigation ul li:focus > ul,
.main-navigation .focus > ul {
border-left: 0;
clip: inherit;
overflow: inherit;
height: inherit;
width: inherit;
}
.main-navigation li ul li a {
background: #efefef;
border-bottom: 1px solid #ededed;
display: block;
font-size: 11px;
font-size: 0.785714286rem;
line-height: 2.181818182;
padding: 8px 10px;
padding: 0.571428571rem 0.714285714rem;
width: 180px;
width: 12.85714286rem;
white-space: normal;
}
.main-navigation li ul li a:hover,
.main-navigation li ul li a:focus {
background: #e3e3e3;
color: #444;
}
.main-navigation .current-menu-item > a,
.main-navigation .current-menu-ancestor > a,
.main-navigation .current_page_item > a,
.main-navigation .current_page_ancestor > a {
color: #636363;
font-weight: bold;
}
.menu-toggle {
display: none;
}
.entry-header .entry-title {
font-size: 22px;
font-size: 1.571428571rem;
}
#respond form input[type=”text”] {
width: 46.333333333%;
}
#respond form textarea.blog-textarea {
width: 79.666666667%;
}
.template-front-page .site-content,
.template-front-page article {
overflow: hidden;
}
.template-front-page.has-post-thumbnail article {
float: left;
width: 47.916666667%;
}
.entry-page-image {
float: right;
margin-bottom: 0;
width: 47.916666667%;
}
.template-front-page .widget-area .widget,
.template-front-page.two-sidebars .widget-area .front-widgets {
float: left;
width: 51.875%;
margin-bottom: 24px;
margin-bottom: 1.714285714rem;
}
.template-front-page .widget-area .widget:nth-child(odd) {
clear: right;
}
.template-front-page .widget-area .widget:nth-child(even),
.template-front-page.two-sidebars .widget-area .front-widgets + .front-widgets {
float: right;
width: 39.0625%;
margin: 0 0 24px;
margin: 0 0 1.714285714rem;
}
.template-front-page.two-sidebars .widget,
.template-front-page.two-sidebars .widget:nth-child(even) {
float: none;
width: auto;
}
.commentlist .children {
margin-left: 48px;
margin-left: 3.428571429rem;
}
}

/* Minimum width of 960 pixels. */
@media screen and (min-width: 960px) {
body {
background-color: #e6e6e6;
}
body .site {
padding: 0 40px;
padding: 0 2.857142857rem;
margin-top: 48px;
margin-top: 3.428571429rem;
margin-bottom: 48px;
margin-bottom: 3.428571429rem;
box-shadow: 0 2px 6px rgba(100, 100, 100, 0.3);
}
body.custom-background-empty {
background-color: #fff;
}
body.custom-background-empty .site,
body.custom-background-white .site {
padding: 0;
margin-top: 0;
margin-bottom: 0;
box-shadow: none;
}
}

/* =Print
———————————————– */

@media print {
body {
background: none !important;
color: #000;
font-size: 10pt;
}
footer a[rel=bookmark]:link:after,
footer a[rel=bookmark]:visited:after {
content: ” [” attr(href) “] “; /* Show URLs */
}
a {
text-decoration: none;
}
.entry-content img,
.comment-content img,
.author-avatar img,
img.wp-post-image {
border-radius: 0;
box-shadow: none;
}
.site {
clear: both !important;
display: block !important;
float: none !important;
max-width: 100%;
position: relative !important;
}
.site-header {
margin-bottom: 72px;
margin-bottom: 5.142857143rem;
text-align: left;
}
.site-header h1 {
font-size: 21pt;
line-height: 1;
text-align: left;
}
.site-header h2 {
color: #000;
font-size: 10pt;
text-align: left;
}
.site-header h1 a,
.site-header h2 a {
color: #000;
}
.author-avatar,
#colophon,
#respond,
.commentlist .comment-edit-link,
.commentlist .reply,
.entry-header .comments-link,
.entry-meta .edit-link a,
.page-link,
.site-content nav,
.widget-area,
img.header-image,
.main-navigation {
display: none;
}
.wrapper {
border-top: none;
box-shadow: none;
}
.site-content {
margin: 0;
width: auto;
}

.entry-header .entry-title,
.entry-title {
font-size: 21pt;
}
footer.entry-meta,
footer.entry-meta a {
color: #444;
font-size: 10pt;
}
.author-description {
float: none;
width: auto;
}

/* Comments */
.commentlist > li.comment {
background: none;
position: relative;
width: auto;
}
.commentlist .avatar {
height: 39px;
left: 2.2em;
top: 2.2em;
width: 39px;
}
.comments-area article header cite,
.comments-area article header time {
margin-left: 50px;
margin-left: 3.57142857rem;
}
}

.page-id-1453 .header-image,
.parent-pageid-1453 .header-image,
.page-id-1453 #secondary,
.parent-pageid-1453 #secondary {
display: none;
}
.page-id-1453 .site-content,
.parent-pageid-1453 .site-content {
float: none;
width: 100%;
}

The code I gave is for page id 266, because it’s in the OP which I think you need changes to apply this page and its child-pages.

Your code use page id = 1453, but there is no page id = 1453 on your site, WordPress doesn’t inject the body class (.page-id-1453 ) into the body tag, it only gets error404 class (not found page), so the CSS code you use will never work.

So just make sure you get the right page id.

FYI: We don’t post big chunk of code like that in the forum. Please read under Post Code Safely and Posting Large Excerpt of Code on this guildlines page

Forum Guidelines

Hi … So sorry about all that code — I was wondering if that would be a problem … I will use Pastebin or Gist from now on.
Before I changed the css page, I did make a sample page with id 1453
It is its own page, with no parent.
… here is that page —
https://zsonics.org/?page_id=1453
Thanks again !

That’s different theme in use, the CSS I provided is for Twentytwelve theme. Each theme has its own CSS class name, one CSS code won’t apply to all themes.

I am embarrassed to have sent you the wrong information.
Here is the correct information —
https://pastebin.com/at6fkwJR
This link (above) goes to the pastebin code for the CSS file for WP theme TwentyTen.
And the page ID is 1453, for this page
https://zsonics.org/?page_id=1453

If you are interested in applying the same CSS code for Twentyten theme, please search for it in the forum or better yet just google it, there are plenty of articles on Twentyten theme. Just search for keywords like How to hide sidebar in Twentyten theme. Look at the selectors in the code I provide, when you get the code for Twentyten theme, just use WP’s page id class and child(sub) page class as shown in my code example.

FYI: I don’t work on Twentyten theme anymore because it’s too old. I’d rather spend time with recent themes. I also would like to encourage you to pick most recent theme for longevity of the project. At certain point in time, theme will be retired. Some really old themes used over at WordPress.COM network get retired and not in used anymore because codes (HTML structure, CSS, and PHP code) when put together in theme won’t be able to keep on updated in a good sense anymore.

Paul, you have persuaded me to update to a newer WP theme. I might try Twenty-Twelve, or Twenty-Sixteen. Thanks again for your help, and good advice — and your patience, too — all are deeply appreciated !