Which Firefox extension checks html markup when you view source?

I used to have a great Firefox add-on for this and I can't remember the name of it..

when you looked at the source it would sit at the bottom (like firebug) and check your HTML markup and suggest things like "doctype given is html4.0, looks like xhtml strict" etc

I thought it was the web developer toolbar but开发者_如何学C that doesn't seem to add anything to the bottom of the source pane?

It seems you are looking for HTML Validator : https://addons.mozilla.org/en-US/firefox/addon/249

It might be the HTML Validator.

this addon http://chrispederick.com/work/web-developer/ in the "tools" menu has an option where you can VALIDATE HTML

It's Web Developer Toolbar: https://addons.mozilla.org/en-US/firefox/addon/60