Hi
While writing this response I discovered you have MS Word formatting code in some of your posts. That is one big NO NO NO – can’t paste directly from Word into the WP editor. That in itself breaks many page displays in IE. The first thing you can do is search through your posts for Word code – it leaves styles called ‘mso’ – that is one way to find it.
Here is an article about a way to get from Word to WP that doesn’t break page displays
https://www.getwordpressed.com/learning-wordpress/paste-easily-to-wordpress-from-ms-word/
I find the most productive way to work with the page validator is to check the box that says Show Source, and refresh. Then the lines of code that the validator sees are displayed after the errors, with line numbers. That lets you correlate the line #’s in validator errors with the section of code that is causing the problem.
A very good idea is, at the top and bottom of your theme’s template file is to add comments like these.. If you are working with
/wp-content/themes/{themename}/index.php, at the top you typically see
something like
<?php get_header(); ?>
<div id="content">
add this
<?php get_header(); ?>
<!-- index.php -->
<div id="content">
and do the same at the bottom – <!– end index.php –>
That way when you View Source to see your page, those comments appear in the code and you know what template file WordPress is using to display that part of your page. You can do this on all the major template files
header.php
index.php
page.php
category.php
archive.php
sidebar.php
footer.php
As you make corrections, refresh the validator to revalidate so you see if your changes fixed anything. Errors generally cascade – when you find the core errors, one fix and correct 25 errors at once.
Another real timesaver is using a programmer’s editor that highlights opening and closing HTML tags – when you point at an opening HTML tag, it becomes highlighted, and also the matching closing tag is highlighted with the same color. This makes it very easy to find mismatched tags. An open source editor that can do this is Notepad++ (Windows only). Copy and paste your code from View Source into the editor, and save the file as an HTML file to activate the tag matching.