These are the extensions I use sometimes. I linked them here to speed up my next Firefox installation. 
- Firefox – the browser itself.

- GMarks – use Google Bookmarks on all my browsers
- Web Developer – identifying CSS elements, testing CSS changes
- Adblock – blocking not only images from certain servers but any kind of object including javascript or flash, based on patterns matching the URL
- Omnibar – merge location bar and search bar
- Status 4 Evar – merge address bar and progress bar
- Show Anchors – show anchors such that you can link to sections within a page
- Universal Edit Button – add an icon to edit wiki pages
- German Dictionary (Switzerland) – hah!
- HTTPS Everywhere
- Echofon – a Twitter client
How to disable compatibility checks in Firefox 6: “Type about:config in the address bar. Right click anywhere on the new window and select New → Boolean from there. A new box will appear where you need to type extensions.checkCompatibility.6.0. Set the value to false.”
Rarely:
- YSlow – provide hints on how to speed up page loading
- Live HTTP Headers – analyzing the HTTP traffic between browser and server; useful for testing HTTP caching code
- Tamper Data – something like Live HTTP Headers
- FireBug – more DOM exploring, Javascript debuggin and more; looks awesome
Here’s how to block content in Firefox with CSS by Workingbath. Basically download two CSS files [1] [2] to your profile/chrome directory and add two lines to the userChrome.css file in that directory:
@import URL("ad_blocking.css");
@import URL("sites.css");I also no longer use the RSS feed reader Sage for which I had written my own patch to support ModWiki.
Other customization:
- use backspace as page-up – in about:config search for backspace, change it to ‘1’
SoftwareUsed