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"
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4. Click on "Make changes and restart"
That's it... your toolbar icons should appear again.