Here are a few tips for keeping what you're doing on your computer private. Great for illegaly playing games in school!
Step 1: Pin Your Tabs
In both Chrome and Firefox, you can pin tabs. This not only shrinks them down to a hard-to-spot size, but also saves them the next time you open the browser. Just right click a tab, and choose "Pin Tab", or "Pin as App Tab".
Step 2: Hide Taskbar
In Windows XP and above, you can set the taskbar to hide itself. To do so, right click on the taskbar, select Properties, and check the box labeled "Auto-Hide the Taskbar". Click Ok. Now, whenever your mouse is away from the very bottom of the screen, the taskbar sinks down, hiding all of your minimized windows until you move your mouse down there.
Step 3: Panic Button
Panic Button is a free extension for both Chrome and Firefox. When you click on it, all of your open tabs disappear and are replaced by either a new tab, or a set of tabs chosen in the options of the button. Click it again to restore your tabs. The only downside of this is that the tabs have to reload, so games, movies, etc, restart from the beginning.