Hardcore FireFox tips and tricks

Any Webdeveloper should use firefox for developing. Why? because of the loads of very usefull extensions. (the headlines are links!)
We’ll start with a built in:

The DOM Inspector
This tool can be found in the menu Tools > DOM Inspector. Or just press ctrl-shift-i.
The DOM Inspector show a tree with all the html elements on the page. You can search for a tag (using the search function) or, click an element on the webpage, and the DOM Inspector shows the details.
When you’re doing lots of css, you can view how firefox renderd the element.
When you’re doing JavaScript the DOM Inspector is very handy! You can view all the javascript objects/atributes of an element. (which saved me a couple of times when I knew about it).
For the windows users: you explicitly need to install the developer tools when installing FireFox

Love it and use it.

Web Developer
A toolbar for FireFox with lots of usable options. You can disable images/javascript and lots of other things from this toolbar with just a few clicks.
Auto fill forms
show information about a lot of elements
clear cache and cookies
outline elements, tables, cells, frames
resize the browser
and validate html and css

This extension should be used by every webdeveloper.

FlashBlock
Block flash movies. Click them to start playing. Easy as that.

Sage
A pretty good RSS reader. Adds a sidebar to firefox (alt-s) which shows the feeds. You can view then in FireFox with costum styles.

Download Them All
Download all the specified image/movies/sounds/any extension from a webpage. Very usefull if you have a lot of files to download from a webpage.

MiniFoxFlat
This is a very small theme. This theme gives some lost space due to toolbars etc, back. Looks good too!