This tip comes from Lifehacker which I thought was pretty cool. Not the easiest hack to try but it’s not that difficult either. To turn on auto-hiding, you have to edit userChrome.css. Before you attempt this hack, use MozBackup to create a backup of your FireFox profile just in case things go amiss.

To make it even easier to perform this trick, I recommend installing the ChromEdit Plus extension. This extension makes browsing around and editing the userChrome.css file a breeze.

Once you have the extension installed, click on TOOLS-ChromEditPlus-ChromEdit. This will open up the editor. Make sure the userChrome.css tab is selected then copy and paste the following code into the text area.

/* Pop-up bookmarks toolbar */ #PersonalToolbar {display: none;} #navigator-toolbox:hover > #PersonalToolbar {display: -moz-box;}

Click SAVE and then RESTART. Your FireFox bookmarks should be hidden. To see them, move your mouse cursor over the address bar. This hack may be annoying for anyone moving their cursor consistently around that area of their browser. However, this is a good hack for those that want a little more screen real estate within FireFox.