only so much. You always need a menu bar and some toolbars, right? Well, not necessarily. Full Screen mode allows you to hide all the clutter and use the entire screen to view a Web site. If you're using Windows, even the taskbar at the bottom is hidden in Full Screen mode. Only a thin version of the Navigation Toolbar remains, as shown in Figure 19-6, so you can access common commands or exit Full Screen mode. Figure 19-6: It's much easier to enjoy this scenic country shot in Full Screen mode. Full Screen mode is especially useful for viewing slideshows or presentations or playing games within the browser, since it offers much more viewing space and less surrounding clutter. Tip Although Full Screen mode hides the menu bar, keyboard shortcuts still work. For example, you can still open the Bookmarks Sidebar by pressing Ctrl+B. Full Screen mode is not available in Firefox for the Mac. To enter Full Screen mode, choose View Full Screen or press F11. Firefox stays in Full Screen mode until you exit it, which you can do by clicking the Restore button in the top-right corner or by pressing F11 again. Warning Don't click the X button to exit Full Screen mode, since doing so closes the window as usual.           Chapter 20: Extending Firefox Overview Software is a compromise. Some parts are fantastic; others are lousy. The features you don't need are front and center, and the ones you're crying out for are nowhere to be found. You wish that button were a menu and that menu a button. It isn't perfect, but it's the best tool out there, quirks and all. Firefox is built to be extensible so you don't have to settle. Unlike most software, Firefox isn't etched in stone. It's more like a collection of building blocks. We developers made the best design we could, but we invite you to move blocks around, remove them altogether, and even add your own. This flexibility is made possible through tiny applications called extensions, which you can install into Firefox. The great thing about extensions is that they don't feel like extensions. Their features are integrated into the main Firefox interface as if they'd been there all along. Likewise, they can alter features that are already built in to Firefox. Extensions don't create a new, separate design; they work with the very blocks that Firefox is made of. Of course, you don't have to make the extensions yourself. The Firefox development community has already created hundreds of them for you, and developers release new ones each day. (I describe ten of the best extensions in Chapter 22, so check it out for a more vivid sense of what extensions can do.) All you have to do is decide what your perfect browser looks like, and then mix and match the extensions that you want. What could be easier? This chapter shows you where to find great extensions, and how to start using them.