Whenever you begin typing a URL in the address box, it tried to find a recently visited page that matches what you are typing. If IE finds a match, it automatically fills in the rest of the address for you. This is not only convenient, it can also be useful if you remember only a part of on Internet address. You can turn the feature on or off from Tools > Internet Options > Advanced. Scroll down to use inline AutoComplete for Web address. Toggle this on or off.
