Google Instant Previews is a new feature that will allow you to view the page you are looking for in a small preview window on the main google page. You can read more about it here. I'm not sure how new this is, there's nothing on the official google blog or anything, but I definitely haven't seen it before.

My first thought was that this might let you view porn in private like you can with Bing :)

Via @johnkoetsier.