This tutorial explains how to prevent Firefox from displaying a list of suggested websites when you type in the address bar. You can apply this setting for specific websites, or all websites in general.
Remove URL From Firefox Address Bar
Open Firefox, and click on Menu > History > View History sidebar. Type the name of a website in the Search field and press Enter. Right-click on the name of the selected website and then select Forget About This Site:
How To Permanently Disable Address Bar Suggestions
Click on Menu > Options, and go to Privacy. Clear the checkboxes labelled History, Bookmarks, and Open tabs shown below When using the location bar, suggest:
Once these options are unchecked, the auto-search options will be disabled.