Right click on the bookmark icon which you want to remove !! Thn a option box will open where you will get delete option !! Now delet it n enjoy............

I want to remove the icon, NOT the bookmark.

You can use this button to go to the currently used Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)

• Create the chrome folder (lowercase) in the <xxxxxxxx>.default profile folder if this folder doesn't exist.
• Use a plain text editor like Text Editor to create a (new) userChrome.css file in this folder (the names are case sensitive).
• Paste the code in the userChrome.css file in the editor window and make sure that the userChrome.css file starts with the default @namespace line.
• Make sure that you select "All files" and not "Text files" when you save the file via "Save file as" in the text editor as userChrome.css..

• http://kb.mozillazine.org/Editing_configuration/Troubleshooting