You can use your PlayStation 3 to surf the Internet, but to view online videos (Youtube, Dailymotion..etc) you will need to install Adobe Flash Player on the PlayStation web browser. Note that: on some consoles Flash Player is already installed!
To install Adobe Flash Player:
The easiest way is to trigger the installation of Flash Player, by visiting a video streaming website, like http://www.youtube.com/.
If Flash is not present, a window opens, prompting you to download the missing plug-ins.