The supported sites should be clearly displayed. Link directly to :- Supported Video Sites http://www.allavsoft.com/how-to/index.html http://www.allavsoft.com/how-to/download-youtube-videos-as-mp4-on-mac-windows.html
OpenID is service that allows you to log-on to many different websites using a single indentity. Find out more about OpenID and how to get an OpenID enabled account.