I’ve never got excited about a web browser before* but Firefox is a good, very good. I definitely recommend it.

It’s been my default for two weeks now and IE will not be coming back. It’s the speed, the tabs, the syntax highlighting in View Source (which can open in a new tab), the built in search, rss bookmarks, yadda.

I am using these exensions in order of preference:

Web Developer 0.8 OMG!
Adds a menu and a toolbar to the browser with various web developer tools. Current tools include converting form POSTs to GETs, hiding images, outlining block level elements, and disabling styles - plus many more.

I use the CSS tools the most

I’ve wanted something like this for years, It Just Works. Any machine** that I use now has all of my bookmarks and it auto updates them all on browser load (although this can be switched off)

ColorZilla
Advanced Eyedropper, ColorPicker, Page Zoomer and other colorful goodies.
A collection of tools, including a Color Picker similar to the one found in Photoshop, an Eyedropper that allows to get a color reading from anywhere in the browser window and a Page Zoomer that allows you to set the page zoom to anything between 20 and 1000 percent.

Get firefox, it’s great and it parses web pages properly

*apart from when I had a two month fad for Opera about 3 years ago

**shouldn’t that be ‘box’