For web application developers, I came across an extremely cool extension for FireFox called WebDeveloper.
This extension adds a new button bar in FireFox with a number of tools including:
- a web form inspector (no more endless printing out POST and GET variables from your server side code, let FireFox tell you what it sent)
- a way to view hidden variables in a page and modify them.
- a way to work with cascading style sheets
- a way to validate HTML, CSS, etc.
You can install WebDeveloper into your copy of FireFox 1.0 by going to the Tools menu and selecting Extensions. Click get more extensions and find WebDeveloper. It's a one click install from there.