how 2 turn javascript on?

cause every time i wanna watch ayoutube video they say your java script is turned off
please help me

http://www.arborday.org/GeneralInfo/enable-jscript.cfm

the problem could also be caused by an outdated or uninstalled flash player, i got that error too when my flash player was not yet installed after format.

you can download the latest flash player from here:
http://www.adobe.com/shockwave/download/index.cgi?Lang=Dutch&P1_Prod_Version=ShockwaveFlas h