If your using Microsoft Internet Explorer, when all of a sudden your status bar, a title bar, and Windows task bar disappear you may have accidentally enabled Internet Explorer full screen mode. You may have accidentally hit your F11 key on your keyboard. This key will turn on Internet Explorer Full screen mode which turns off a Status Bar, a Title Bar, Windows Task Bar, and then compresses all remaining toolbars into one slim row.
If your having this problem try hitting an F11 key to turn off full screen mode. You can easily toggle on or off Internet Explorer full screen mode by pressing your F11 key.