Google launched a new behavior on the search page that hides everything but the logo and search form on load, and fades in the rest of the surrounding interface when the user moves the mouse. The idea is to give focus to search for the primary use case, where a user hits the page and starts typing without moving the mouse. They talk about the new behavior on the Google Blog.
http://googleblog.blogspot.com/2009/12/now-you-see-it-now-you-dont.html?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+blogspot%2FMKuf+%28Official+Google+Blog%29