important facebook question?

[Shanes Unicorn]

does facebook have viruses on it? every time i get on my computer starts slowing down and then freezes
i do play the games on there but before i shut the computer down i clean the cookies out and clear all the data. but it still starts to mess up and now its getting worse i do the virus scan on it about one time a week but nothing shows up and it says there is nothing wrong with my computer. except for this morning it showed a virus and the only thing i use the computer for is for three things. facebook (i stay on there about all day), to email my grandma and to get on yahoo answers. and of course it only does this when im on facebook.
i know myspace has viruses my odl computer didnt have a viruse thing ecause it ran out and i was on myspace for im guessing 5mins and it crashed