Michael Tumlad

Counts the title, content, and excerpt characters while you edit your post or page via the admin screen. Even counts the title characters while in Quick Edit!
Decon(structed) Character Counter is a real-time character counter
<ul>
<li>for title (post or page)</li>
<li>for content (post or page)</li>
<li>for excerpt (post or page)</li>
<li>for biographical info (user)</li>
<li>for Quick Edit title (post or page)</li>
</ul>
Works out of the box and seamlessly integrates with your WordPress admin dashboard so you can focus on writing.
Also comes with a real-time SEO-friendly reminder, just in case.

Decon Character Counter

Counts the title, content, and excerpt characters while you edit your post or page (even in Quick Edit).

edik

Some WordPress functions outputs character entity references. The most of these are not allowed in XHTML. So if your WordPress installation uses the mime type ‘application/xhtml+xml’, the generated sites could have invalid xhtml code and the browser would display the syntax error page.
Convertentity converts all entity references into their corresponding characters with the exception of the references for the following characters: ‘<>&”
Theses references are the only ones which are allowed in XHTML.

Convertentity

Converts all character entity references, which are forbidden in XHTML, into their corresponding characters.

Decon Character Counter vs Convertentity