Plzzzz help me guyzzzzzzzzz for java script

Hello,
i have java script in my pc (WINDOW XP) yet when i try to download youtube videos it apear a error and saying {click here to download java script} i have java and i tried very much but it does not work plz help me
this is my email adress {santosh.thorani@yahoo.com}
plzzzzzzzzzz help me
i will be very thankful for that