I didn’t really know how it was lost. All I can remember is I run the Firefox updates and when I try to get back to browser, the Web Developer Toolbar is missing. Even in the Tools menu, it is missing. After trying to disable-enable it and uninstall-install it, I tried searching Google and finally got this blog.
After reading the post and going through the comments I tried to disable the Skype extension. Whew! Great it worked! I don’t know what’s wrong with the Skype extension. But as far as I can remember both addons are running together. Anyways, I can leave without the Skype addon.