now download youtube videos in mp4 format and HD quality,
so
open ur Firefox browser and click 3rd tool bar and click "New Bookmarks"
now a new window will open,see figure
in the "Name" box write whatever u like! such as"Get youtube videos"
in "Location" box copy and paste the following java code
javascript:if(document.location.href.match(/http:\/\/[a-zA-Z\.]*youtube\.com\/watch/)){document.location.href='http://www.youtube.com/get_video?fmt='+(isHDAvailable?'22':'18')+'&video_ id='+swfArgs['video_id']+'&t='+swfArgs['t']}
and click "ADD"
now open any youtube video and click on "get youtube video" ur downloading will start in mp4 format and u can also play songs in ur mobile.
Bookmarks