If you type in to Google search do a barrel role the page will spin. It's a Google Easter Egg special effect.
I've also seen a YouTube video with someone saying they can make the browser spin, (browser or just web page?). But I didn't watch it all.
Not sure if this is malware related. Just now, when I enter a search string on www.google.com, results are listed, but the image on the browser spins around in a circular motion. The spinning stops when I stop entering, and resumes when I type something again. After restarting my browser I don't notice it anymore.
I am using Win 7, Firefox 8.0.1. My latest scans (Microsoft Security Essentials) is clean. Thanks.