I don't know if this should go here. But if you are a web developer and you are using Firefox (as you should be!) I would really advise download the Web Developer extension. It's very useful.
It allows you to send any page to a validation check, CSS and XHTML, looks at the CSS pages and lets you play with them as well. It's got lots of other features as well. It's definitely worth the download.
Web Developer Extension
