https://addons.mozilla.org/en-US/firefox/addon/7884
This is a extension for firefox3.0
You can hide Bookmarks Toolbar, Bookmarks Menu and Unsorted Bookmarksin the sidebar.
Hiding items are specified by option.
In addition,
The extension confirmed that it functioned only on WindowsXP
Because I do not have the other OS. I can not confirm on the other OS.
However, this may work on the other OS because I do not use the function that is peculiar to the OS.
As for me, English is not a first language.
Please use a simple sentence structure and vocabulary as possible when you reply to me.