A. When you view a website in compatibility mode, it automatically gets added to a list of sites to always render using compatibility mode. If you leave the site and come back to it, the compatibility mode will still be used. You can easily turn it off by deselecting the compatibility mode button next to the URL, but you can also look at all your compatibility settings by selecting Compatibility View Settings from the Page menu in IE. This will bring up a dialog that lists all the sites that will use compatibility mode. You'll see options to control how intranet sites are viewed and if Microsoft's lists of sites that are known to benefit from compatibility mode should be used.

IE 8 Compatibility Settings