Here’s a quick way to check any page for valid markup.

First, create a new bookmark on the toolbar of your web browser. You can usually right-click on the toolbar, and choose “add bookmark”.

Next, give your new bookmark the name:
The W3C Markup Validation Service

For the location, use:
javascript:location.href=’http:/’+’/validator.w3.org/check?uri=’+window.location.href.replace(’#’,’|’);

This works in Firefox quite well. I also works in IE 6 if you can figure out how to add a link to your toolbar.