When you get a link to a YouTube video to your Gmail account, wouldn't it be nice to view the video right then and there without opening a new tab or window? You're not the only one who thinks so. A new Gmail Labs feature enables just that.
Turn on the new feature by clicking on "Settings" in the top right corner of your Gmail page. Then look for "Labs." Previews for Picasa, Flickr and Yelp have been added as well.