Um... That is old and outdated. It can't run the new Flash and Shockwave which is what you are going to need if you want to view Youtube videos (You don't need Shockwave to view youtube videos. xD)
To Opera users: Isn't Opera the same as firefox except with a weird gui? :P
To Chrome users: I will give you a fair warning, that google uses Chrome to collect your personal info to market you stuff that might interest. Not making this up.
Internet Explorer Users (Of any version): What the crap are you doing using that piece of crap? I suggest to get another browser. Anything is better than that piece of Giygas's crap!