tompahoward

The Tiny XHTML plugin re-adds the xhtmlxtras plugin support to the TinyMCE Rich Visual Editor. 
The TinyMCE table plugin is normally bundled with TinyMCE, but it has be removed from the 
version within WordPress. This plugin puts it back in.
The xhtmlxtras TinyMCE plugin allows you to control common attributes, such as class, id, lang, onclick, etc. 
It also provides buttons for creating cite, ins, del, abbr, and acronym elements.
Most of the credit for this plugin belogns to [Moxiecode Systems] (http://tinymce.moxiecode.com/ ), 
who wrote the Table plugin for TinyMCE, which this plugin uses.
<h3>Release Notes</h3>
<ul>
<li>0.0.2
<ul>
<li>Added workaround for TinyMCE compressor issues.</li>
</ul>
</li>
<li>0.0.1
<ul>
<li>Fixed defect in link to xhtmlxtras stylesheet</li>
</ul>
</li>
<li>0.0.0
<ul>
<li>Initial Release</li>
</ul>
</li>
</ul>

Tiny XHTML

The Tiny XHTML plugin re-adds the xhtmlxtras plugin to the TinyMCE Rich Visual Editor

Nikoya

Check the doctype validity using W3c validator (html , xhtml , … ) when creating or updating page / post / custom post type and show the result in backend 
It show the result in back-end in sortable column, a link is add to the w3c for all file to help you to correct html error.
Very easy to see if a post / page is valid or not.
This plugin can check the W3C validity of your page / post or custom post type even if the site is not accessible from the Internet (if you work on local system for example)

(x)html easy validator

Check the doctype validity using W3c validator (html , xhtml , ... ) when creating or updating  page / post / custom post type and show the result in  …

Tiny XHTML vs (x)html easy validator