I got a good one for you gurus out there or for the plugin author, should he read this post...
A site (syncbox.com) has been a WordPress site for years. I keep it updated. It's using 2.8.4 and isn't using the basic theme markup as it is a totally custom layout with WordPress logic inserted and used as a CMS.
While validating said xhtml-strict markup (again, as it used to be pretty valid) I got 3 errors. Two I don't really care about but this one intrigued me:
<title>S Y N C B O X web design & development</title>
This message may appear in several cases:
* You tried to include the "<" character in your page: you should escape it as "<"
* You used an unescaped ampersand "&": this may be valid in some contexts, but it is recommended to use "&", which is always safe.
* Another possibility is that you forgot to close quotes in a previous tag.
Here's how the title is being generated via WordPress functions:
<title><?php bloginfo('name'); ?> <?php if ( is_single() ) { ?> » Blog Archive <?php } ?> <?php wp_title(); ?></title>
I hadn't seen this before, so I suspected a recent plugin (TGIF SEO plugin) and so disabled it and the error went away. Well, OK... but WHY?
And while sourcing the why of it... I have to ask HOW?!!? Because... I cannot find that ampersand anywhere! I cannot figure out where the "web design & development" data is being pulled from... It's not in my template files at all (so not hard-coded in)... and it's not in the site name or site description fields in my General Settings!
Where else can I look? I honestly think I may have had "web design & development" in the tagline at one time, but it's not in there NOW as I checked directly in the database options table... in the blogdescription, which has "design | develop | deploy" in it.
TOO WEIRD!