semilogic theme

Can anyone help me sort out a issue with this theme, I need to alter the style.css to ensure that it is centered and no more than 790 pixels wide or if this is not possible 100%

the current style.css is attached below

/*
Theme Name: Semiologic
Theme URI: https://www.semiologic.com/software/sem-theme/
Description: The Semiologic theme • Terms of use
Version: 4.1
Author: Denis de Bernardy
Author URI: https://www.mesoconcepts.com
*/

/*
Terms of use
————

This software is copyright Mesoconcepts Ltd, and is distributed under the terms of the Mesoconcepts license. In a nutshell, you may freely use it for any purpose, but may not redistribute it without written permission.

https://www.semiologic.com/legal/license/
**/

/*
#
# DO NOT EDIT THIS FILE
# ———————
# The Semiologic theme features a custom.css feature. This allows to edit the skin
# without editing its css files. That way, you won’t need to worry about loosing
# your changes when you upgrade your site.
#
# You’ll find detailed sample files in the skins directory
#
*/

/* body */

body
{
background-color: white;
color: black;
}

/* margins */

form,
object,
param,
embed,
.sidebar ul,
.sidebar li
{
margin: 0px;
padding: 0px;
}

div.spacer
{
margin: 0px;
padding: 0px;
}

div.pad
{
padding: 4px 8px;
}

.main,
.sidebar
{
overflow: hidden;
}

.header_bg #header div.pad,
.header_img #header div.pad
{
background-repeat: no-repeat;
padding: 0px;
margin: 0px;
border: none;
}

#header_nav,
#footer_nav,
#copyright_notice
{
margin-top: 3px;
margin-bottom: 3px;
}

.sidebar ul,
.sidebar li
{
list-style-type: none;
}

.sidebar li ul,
.sidebar li li
{
list-style-type: square;
}

.sidebar li li
{
margin-left: 1.5em;
}

.sidebar li .sem_subscribe_me ul,
.sidebar li .sem_subscribe_me li,
#democracy ul,
#democracy li
{
margin-left: 0px;
list-style-type: none;
}

/* layout */

#footer,
#credits,
div.spacer
{
clear: both;
}

#header_nav,
#copyright_notice,
.mse #wrapper,
.mse #main,
.sme #wrapper,
.sme #sidebar,
.ems #ext_sidebar,
.ems #main,
.esm #ext_sidebar,
.esm #sidebar,
.ms #main,
.sm #sidebar,
.me #wrapper,
.em #ext_sidebar
{
float: left;
}

#search_form,
#footer_nav,
.mse #ext_sidebar,
.mse #sidebar,
.sme #ext_sidebar,
.sme #main,
.ems #wrapper,
.ems #sidebar,
.esm #wrapper,
.esm #main,
.ms #sidebar,
.sm #main,
.me #ext_sidebar,
.em #wrapper
{
float: right;
}

/* narrow3 width */

.narrow3 #ext_wrapper
{
width: 770px;
margin: 10px auto;
}

.narrow3 #wrapper
{
width: 590px;
}

.narrow3 #main
{
width: 410px;
}

.narrow3 #ext_sidebar,
.narrow3 #sidebar
{
width: 178px;
}

/* narrow2s width */

.narrow2s #ext_wrapper
{
width: 590px;
margin: 10px auto;
}

.narrow2s #main
{
width: 410px;
}

.narrow2s #ext_sidebar
{
display: none;
}

.narrow2s #sidebar
{
width: 178px;
}

/* narrow2e width */

.narrow2e #ext_wrapper
{
width: 770px;
margin: 10px auto;
}

.narrow2e #wrapper
{
width: 590px;
}

.narrow2e #ext_sidebar
{
width: 178px;
}

.narrow2e #sidebar
{
display: none;
}

/* narrow1 width */

.narrow1 #ext_wrapper
{
width: 590px;
margin: 10px auto;
}

.narrow1 #ext_sidebar,
.narrow1 #sidebar
{
display: none;
}

/* wide3 width */

.wide3 #ext_wrapper
{
width: 970px;
margin: 10px auto;
}

.wide3 #wrapper
{
width: 770px;
}

.wide3 #main
{
width: 560px;
}

.wide3 #ext_sidebar,
.wide3 #sidebar
{
width: 198px;
}

/* wide2s width */

.wide2s #ext_wrapper
{
width: 770px;
margin: 10px auto;
}

.wide2s #main
{
width: 560px;
}

.wide2s #ext_sidebar
{
display: none;
}

.wide2s #sidebar
{
width: 198px;
}

/* wide2e width */

.wide2e #ext_wrapper
{
width: 970px;
margin: 10px auto;
}

.wide2e #wrapper
{
width: 770px;
}

.wide2e #ext_sidebar
{
width: 198px;
}

.wide2e #sidebar
{
display: none;
}

/* wide1 width */

.wide1 #ext_wrapper
{
width: 770px;
margin: 10px auto;
}

.wide1 #ext_sidebar,
.wide1 #sidebar
{
display: none;
}

/* flex3 width */

.flex3 #ext_wrapper
{
margin: 10px 10px;
}

.flex3 #wrapper,
.flex3 #main
{
width: 75%;
}

.flex3 #ext_sidebar,
.flex3 #sidebar
{
width: 18%;
}

/* flex2s width */

.flex2s #ext_wrapper
{
margin: 10px 10px;
}

.flex2s #main
{
width: 75%;
}

.flex2s #ext_sidebar
{
display: none;
}

.flex2s #sidebar
{
width: 18%;
}

/* flex2e width */

.flex2e #ext_wrapper
{
margin: 10px 10px;
}

.flex2e #wrapper
{
width: 75%;
}

.flex2e #ext_sidebar
{
width: 18%;
}

.flex2e #sidebar
{
display: none;
}

/* flex1 width */

.flex1 #ext_wrapper
{
margin: 10px 10px;
}

.flex1 #ext_sidebar,
.flex1 #sidebar
{
display: none;
}

/* aligns */

#tagline
{
text-align: right;
}

#search_form
{
text-align: right;
vertical-align: middle;
}

#copyright_notice
{
vertical-align: middle;
}

#footer_nav
{
text-align: right;
vertical-align: middle;
}

.entry_actions,
.comment_actions
{
text-align: right;
}

/* text block margins */

div.entry,
div.entry_body,
div.entry_meta,
div.entry_actions
div.comment,
div.comment_body
{
margin-top: .5em;
margin-bottom: .5em;
padding-top: 0px;
padding-bottom: 0px;
}

div.entry
{
margin-top: .5em;
margin-bottom: 2em;
}

div.entry_header,
div.comment_header,
.sidebar li
{
margin-top: 1.5em;
margin-bottom: .5em;
padding-top: 0px;
padding-bottom: 0px;
}

div.entry_header h2,
div.entry_header h1,
div.entry_author,
div.entry_date,
div.entry_nav,
div.entry_tags,
div.comment_header h2,
div.comment_header h3
{
margin-top: .2em;
margin-bottom: .2em;
padding-top: 0px;
padding-bottom: 0px;
}

h1,
h2,
h3
{
margin-top: 1.5em;
margin-bottom: 1.2em;
padding-top: 0px;
padding-bottom: 0px;
}

.header_bg #tagline h2,
.header_img #tagline h2
{
padding: 1.5em 8px 0em 8px;
margin-top: 0px;
margin-bottom: 1.2em;
}

.header_bg #sitename h1
{
padding: 1.5em 8px 1.2em 8px;
margin-bottom: 0px;
}

.header_bg #sitename,
.header_bg #sitename h1
{
margin-top: 0px;
margin-bottom: 0px;
}

.header_bg #tagline,
.header_bg #tagline h2
{
margin-top: 0px;
margin-bottom: 0px;
}

.header_img #sitename h1
{
margin: 0px;
padding: 0px;
}

p,
ul,
.sidebar li ul,
ol,
dl,
pre,
hr
{
margin-top: 1.2em;
margin-bottom: 1.2em;
padding-top: 0px;
padding-bottom: 0px;
}

blockquote
{
background: url(img/blockquote.gif) 6px 6px no-repeat;
margin-left: 0px;
margin-right: 0px;
padding: 10px 10px 10px 60px;
}

pre
{
margin-left: 0px;
margin-right: 0px;
padding: 10px 10px 10px 10px;
}

table,
li,
.sidebar li li,
.sidebar li li ul,
dt,
dl
{
margin-top: .2em;
margin-bottom: .2em;
padding-top: 0px;
padding-bottom: 0px;
}

/* inline menus */

.inline_menu ul,
.inline_menu li
{
display: inline;
list-style-type: none;
margin: 0px;
padding: 0px;
}

.inline_menu li
{
margin-left: 2px;
margin-right: 2px;
}

/* admin links */

.admin_link
{
font-weight: normal;
font-size: small;
}

/* links */

a img
{
border: none;
}

a em
{
font-style: normal;
color: firebrick;
}

a,
h1 .admin_link a,
h2 .admin_link a
{
color: blue;
text-decoration: underline;
}

h1 a,
h2 a
{
text-decoration: none;
color: black;
}

h1 a.external,
h2 a.external
{
background: none;
padding-right: 0px;
}

a:hover,
.admin_link a:hover
{
color: firebrick;
}

/* override external links */

.header .external,
.sidebar .external,
.footer .external
{
background-image: none;
padding-right: 0px;
}

/* credits */

#credits
{
margin: 10px auto;
text-align: center;
font-size: small;
}

/* comment form */

#author,
#email,
#url,
#comment
{
width: 90%;
}

/* gravatars */

img.gravatar
{
float: left;
margin: .2em 1em;
}

/* translator bar */

.narrow3 #translator_bar,
.narrow2e #translator_bar
{
width: 770px;
margin: 10px auto;
}

.narrow2s #translator_bar,
.narrow1 #translator_bar
{
width: 590px;
margin: 10px auto;
}

.wide3 #translator_bar,
.wide2e #translator_bar
{
width: 970px;
margin: 10px auto;
}

.wide2s #translator_bar,
.wide1 #translator_bar
{
width: 770px;
margin: 10px auto;
}

.flex3 #translator_bar,
.flex2e #translator_bar,
.flex2s #translator_bar,
.flex1 #translator_bar
{
margin: 10px 10px;
}

#translator_bar table
{
margin-left: auto;
margin-right: 0px;
}

/* floating images */

.entry_body img
{
margin: .2em 1em;
}

/* gallery class */

.gallery
{
overflow: hidden;
}

.gallery p
{
text-align: center;
}

.gallery img
{
border: outset 1px;
margin: .2em auto;
}

/* ad */

div.ad
{
border: solid 1px lavender;
background-color: ghostwhite;
color: black;
padding: 0px 10px;
clear: both;
}

.main div.ad
{
margin: .5em 0px;
}

/* widgets */

#calendar h2,
#google-search h2
{
display: none;
}

/* calendar */

#wp-calendar
{
width: 100%;
border-collapse: collapse;
}

#wp-calendar th,
#wp-calendar td
{
padding: 1px 2px;
text-align: center;
}

#wp-calendar #prev
{
text-align: left;
padding-right: 3px;
}

#wp-calendar #next
{
text-align: right;
padding-left: 3px;
}

#today
{
font-weight: bold;
}

/* tables */

.main table
{
width: 100%;
}

.main th,
.main td
{
padding: 1px 2px;
}

/* font face */

.antica,
.antica h1,
.antica h2,
.antica h3,
.antica p,
.antica li,
.antica dt,
.antica dd,
.antica th,
.antica td,
.antica input,
.antica select,
.antica button,
.antica textarea
{
font-family: Book Antica, Times, Serif;
}

.arial,
.arial h1,
.arial h2,
.arial h3,
.arial p,
.arial li,
.arial dt,
.arial dd,
.arial th,
.arial td,
.arial input,
.arial select,
.arial button,
.arial textarea
{
font-family: Arial, Helvetica, Sans-Serif;
}

.bookman,
.bookman h1,
.bookman h2,
.bookman h3,
.bookman p,
.bookman li,
.bookman dt,
.bookman dd,
.bookman th,
.bookman td,
.bookman input,
.bookman select,
.bookman button,
.bookman textarea
{
font-family: Bookman Old Style, Times, Serif;
}

.comic,
.comic h1,
.comic h2,
.comic h3,
.comic p,
.comic li,
.comic dt,
.comic dd,
.comic th,
.comic td,
.comic input,
.comic select,
.comic button,
.comic textarea
{
font-family: Comic Sans MS, Helvetica, Sans-Serif;
}

.corsiva,
.corsiva h1,
.corsiva h2,
.corsiva h3,
.corsiva p,
.corsiva li,
.corsiva dt,
.corsiva dd,
.corsiva th,
.corsiva td,
.corsiva input,
.corsiva select,
.corsiva button,
.corsiva textarea
{
font-family: Monotype Corsiva, Courier, Monospace;
}

.courier,
.courier h1,
.courier h2,
.courier h3,
.courier p,
.courier li,
.courier dt,
.courier dd,
.courier th,
.courier td,
.courier input,
.courier select,
.courier button,
.courier textarea
{
font-family: Courier New, Courier, Monospace;
}

.garamond,
.garamond h1,
.garamond h2,
.garamond h3,
.garamond p,
.garamond li,
.garamond dt,
.garamond dd,
.garamond th,
.garamond td,
.garamond input,
.garamond select,
.garamond button,
.garamond textarea
{
font-family: Garamond, Times, Serif;
}

.georgia,
.georgia h1,
.georgia h2,
.georgia h3,
.georgia p,
.georgia li,
.georgia dt,
.georgia dd,
.georgia th,
.georgia td,
.georgia input,
.georgia select,
.georgia button,
.georgia textarea
{
font-family: Georgia, Times, Serif;
}

.tahoma,
.tahoma h1,
.tahoma h2,
.tahoma h3,
.tahoma p,
.tahoma li,
.tahoma dt,
.tahoma dd,
.tahoma th,
.tahoma td,
.tahoma input,
.tahoma select,
.tahoma button,
.tahoma textarea
{
font-family: Tahoma, Helvetica, Sans-Serif;
}

.times,
.times h1,
.times h2,
.times h3,
.times p,
.times li,
.times dt,
.times dd,
.times th,
.times td,
.times input,
.times select,
.times button,
.times textarea
{
font-family: Times New Roman, Times, Serif;
}

.verdana,
.verdana h1,
.verdana h2,
.verdana h3,
.verdana p,
.verdana li,
.verdana dt,
.verdana dd,
.verdana th,
.verdana td,
.verdana input,
.verdana select,
.verdana button,
.verdana textarea
{
font-family: Verdana, Helvetica, Sans-Serif;
}

pre,
code
{
font-family: Courier New, Courier, Monospace;
}

/* font size */

h1
{
font-size: large;
}

h2,
#wp-calendar caption
{
font-size: medium;
font-weight: bold;
}

body,
h3,
p,
li,
dt,
dd,
table,
th,
td,
input,
select,
button,
textarea,
pre,
code
{
font-size: small;
}

.antica h1,
.corsiva h1,
.garamond h1,
.times h1
{
font-size: x-large;
}

.antica h2,
.antica #wp-calendar caption,
.corsiva h2,
.corsiva #wp-calendar caption,
.garamond h2,
.garamond #wp-calendar caption,
.times h2,
.times #wp-calendar caption
{
font-size: large;
font-weight: bold;
}

body.antica,
.antica h3,
.antica p,
.antica li,
.antica dt,
.antica dd,
.antica th,
.antica td,
.antica input,
.antica select,
.antica button,
.antica textarea,
body.corsiva,
.corsiva h3,
.corsiva p,
.corsiva li,
.corsiva dt,
.corsiva dd,
.corsiva th,
.corsiva td,
.corsiva input,
.corsiva select,
.corsiva button,
.corsiva textarea,
body.garamond,
.garamond h3,
.garamond p,
.garamond li,
.garamond dt,
.garamond dd,
.garamond th,
.garamond td,
.garamond input,
.garamond select,
.garamond button,
.garamond textarea,
body.times,
.times h3,
.times p,
.times li,
.times dt,
.times dd,
.times th,
.times td,
.times input,
.times select,
.times button,
.times textarea
{
font-size: medium;
}

#sitename h1
{
font-size: x-large;
}

.tahoma h1,
.tahoma h2,
.verdana h1,
.verdana h2
{
font-family: Georgia, Times, Serif;
}

.antica #sitename h1,
.corsiva #sitename h1,
.garamond #sitename h1,
.georgia #sitename h1,
.times #sitename h1
{
font-family: Tahoma, Helvetica, Sans-Serif;
font-size: x-large;
}

/* entry_author_image */

.entry_author_image
{
float: left;
margin: .2em 1em;
}

/* cc_license */

.license_block
{
margin-right: auto;
margin-left: auto;
text-align: center;
}

/* marker, large buttons */

.marker
{
background-color: yellow;
color: black;
}

.large_button
{
width: 240px;
height: 160px;
margin: 2em auto;
background-repeat: no-repeat;
cursor: pointer;
font-family: Tahoma, Helvetica, Sans-Serif;
}

.large_button .button_tag
{
font-size: 24pt;
padding: 24px 16px 14px 16px;
font-weight: bold;
color: firebrick;
}

.large_button .button_action
{
font-size: 24pt;
padding: 24px 24px;
text-align: center;
font-weight: bold;
color: black;
font-variant: small-caps;
}

/* sell page related stuff */

body.sell #ext_wrapper
{
width: 590px;
margin: 10px auto;
}

body.sell #ext_sidebar,
body.sell #sidebar,
body.sell #sem_admin_menu

{
display: none;
}

body.sell
{
background-color: steelblue;
color: black;
}

body.sell #ext_wrapper,
body.sell #wrapper,
body.sell #main,
body.sell #body
{
background-image: none;
background-color: white;
color: black;
border: none;
}

body.sell #ext_wrapper
{
border: inset 1px;
}

div.sell
{
margin-left: 1em;
margin-right: 1em;
}

div.side_testimonials
{
float: right;
padding: 0px 1em;
margin-left: 1em;
background-color: antiquewhite;
color: black;
width: 160px;
}

.sell blockquote
{
background-color: antiquewhite;
color: black;
}

body.sell a
{
color: blue;
text-decoration: underline;
}

body.sell a:hover
{
color: firebrick;
}

.sell h1
{
color: #d00;
font-weight: 900;
font-family: Tahoma, Helvetica, Sans-Serif;
font-size: 24pt;
text-align: center;
margin-left: 1em;
margin-right: 1em;
}

.sell h2
{
color: black;
font-weight: 900;
font-family: Tahoma, Helvetica, Sans-Serif;
font-size: 16pt;
text-align: center;
}

.side_testimonials h2
{
margin-top: 2.5em;
color: black;
font-weight: 900;
font-family: Tahoma, Helvetica, Sans-Serif;
font-size: 10pt;
text-align: center;
}

body.sell,
.sell h3,
.sell p,
.sell li,
.sell dl,
.sell dt,
.sell dd,
.sell table,
.sell th,
.sell td,
.sell input,
.sell select,
.sell button,
.sell textarea,
.sell pre,
.sell code
{
font-family: Times New Roman, Georgia, Garamond, Times, Serif;
font-size: 13pt;
}

body.sell .gallery p
{
font-family: Tahoma, Helvetica, Sans-Serif;
font-size: 11pt;
}

body.sell p strong
{
font-weight: 900;
}

.side_testimonials h3,
.side_testimonials p,
.side_testimonials li,
.side_testimonials dl,
.side_testimonials dt,
.side_testimonials dd,
.side_testimonials table,
.side_testimonials th,
.side_testimonials td,
.side_testimonials input,
.side_testimonials select,
.side_testimonials button,
.side_testimonials textarea,
.side_testimonials pre,
.side_testimonials code
{
font-family: Tahoma, Helvetica, Sans-Serif;
font-size: 10pt;
}

body.sell .side_testimonials a,
body.sell .testimonials a,
body.sell .testimonial a,
body.sell a.testimonial
{
color: black;
text-decoration: none;
}

.order_form
{
margin: 2em 3em;
padding: 1em 2em;
border: solid 1px #ccc;
background-color: #eee;
}