You can try the solutions here to remove skippity and the toolbar. http://kb.mozillazine.org/Uninstalling_toolbars

If they were installed without your knowledge it may be because you installed the Download YouTube Videos + Flash Video Downloader extension, according to several users reviews of that addon skippity and the toolbar are being installed by the addon without their knowledge or choice. If that is the case, you should remove that addon as well, otherwise it may upgrade and reinstall skippity.

The real solution.... works on all versions of Firefox even with the plugins active the bar will not come back. A quick 10 step process:

1. Open a new tab
2. In the address bar type "about:config"
3. Click the button "I'll be careful, I promise!"
4. In the search bar in the top type "skipity" (Yes, only 1 p in skipity)
5. Under preference name go to "extensions.vidbar.skipitysearchset"
6. Right click and toggle to "False"
7. Under preference name go to "extensions.vidbar.skipityversion"
8. Right click and toggle to "False"
9. Close tab
10. Close Firefox