The Web Developer Firefox extension is a must have for any web developer. If you haven’t already, download FireFox.

Then grab this ad on, which lets you see the css hierarchy as you put your mouse over objects on the page. You can also automatically populate forms, turnon css classes on the page, to see which class something is. Also outlining of various objects, like table cells.

You can disable cookies, clear cache, etc for that one page. Check it out, see the features here.