Each time I make a query in the Address bar, there's a drop down menu that appears (full of suggestions). Is there any solution to disable it.
Under Firefox 3, if you want to delete an individual entry from the History, just highlight it (either in the History sidebar or in the address bar drop-down menu) and press Shift+Delete. Gone, never to bother you again! This method works for Windows users but won't work for Mac users.
For Mac user:
Start up Firefox
Before removing your bookmarks make a backup or export your current Bookmarks list to load them back afterwards
Clear all your private data (Tools > Clear Private Data...)
Go to your address / URL Bar and enter "about:config" and click the button "I'll be carefull, I promise!"
Change the values of the following entries to these settings: