add-ons

I found following extensions from firefox, which i found really useful.

Might be you are already using some extensions. If not, they are worth downloading and using...

measureIT -- measure pixel of objects on screen
screen grab -- grab screen (instead of using printscreen)
linkification -- convert text links into real URL
forecastfox -- weather information
web developer -- Loads of useful tools(Most important)
view rendered source chart -- important source chart
del.icio.us -- Bookmarks with Tags, very imp
flashGot -- download manager
pdf download
IE Tab -- open IE tab in firefox to test sites