Along with the ‘Go’ Button and the Bookmark ‘Star’ (Fx 3) buttons there is also a ‘Live Feed’ button to add clutter to the address bar:

To remove the ‘Live Feed’ Button use ChromEdit and add the following lines to your userChrome.css file:

/* Remove live feed icon in Address url toolbar */
#feed-button {
display: none !important;
}

Once you have added these lines, click Save, then Restart; the ‘Live Feed’ button will be gone when Firefox restarts. Note: This tweak works for Fx 2 & 3.

Tip Source: Eric Wendelin’s Blog