Gmail now detects and displays content previews on YouTube, Picasa, Flickr, and Yelp [Gmail Labs]

Google announced today is the addition of four experimental new features in Gmail Labs that allow Gmail to automatically detect links in emails and display video content, photos and ratings within the messages themselves.

In addition to the Gmail technology that detects the delivery status of deliveries, addresses, and event information, Google Mail users can now activate four new content detection systems and explore their own content without having to click on new links.

To enable the new feature, just go to the settings page, click on the “Gmail Labs” tab and select the desired options. That done, click the save button. If you're using Gmail Offline, the new settings take a few minutes to fully apply.