For some unknown reason my web developer and delicious firefox toobars disappeared, I could see the space where they used to be but no icons or anything was there. I tried with the view toolbars menu , checking and unchecking to hide and show them, but that didn't work. Finally I found the solution, firefox have an option called firefox safemode
http://kb.mozillazine.org/Safe_mode which allows us to troubleshoot some problems (like this one), all you have to do is:
1. Close any running intance of firefox.
2. Type this command :
firefox -safe-mode
For more info for different OSs
check here3. Then check the box for "Reset toolbars and controls"
4. Click on "Make changes and restart"
That's it... your toolbar icons should appear again.