Youtube launched a new and upgraded mobile video website written in HTML5: m.youtube.com. The new website sports a couple of new features, including high-quality video playback in the browser using HTML5. Of course, you will need a browser that supports the HTML 5 <video> tag. Devices from Apple: iPhones, iPads and Android phones all support the HTML5 mark-up.
When you would click on a video in the old mobile Youtube site, you would be taken outside of the site and redirected to the player app for Youtube in order to watch the video. Now, you can watch videos right from the browser without the redirect.