Web browsers allow users to customize menus and toolbars for their convenience. Unfortunately, commands turning off features like the address bar can be pressed by accident, leaving the program unusable.
In versions 7 and 8 of Microsoft's Internet Explorer, the address bar cannot be disabled. For earlier versions, enter the "View" menu, then open "Toolbars" and check the "Address Bar" option.
Mozilla's Firefox browser calls its address bar the "Navigation Bar," but the option is otherwise the same. Open the "View" menu, scroll over "Toolbars" and check the "Navigation Bar" option.
On a Macintosh running Safari, open the "View" menu, and select the option titled "Show/Hide Toolbar." Safari also offers a keyboard shortcut, activated by holding the "Command" and "Shift" keys and pressing "," without quotes.
Google's Chrome browser does not allow the address bar to be closed, but in full-screen mode it will not be visible. Toggle this mode on or off by pressing the "F11" key.