random js ads?

i have some ads codes
4 example adbrite YPN adsense clicksor

and this is a js file:
document.write('adbrite');
document.write('YPN');
document.write('ADSENSE');
document.write('clicksor');

but how i can show them randomly?(i want show a ad in my site randomly - for example for first visit my blog show adbrite ads and for second visitor show clicksor ad...)

how i can do it?

 

What is your site scripts (server side such php, asp or html only)

 

If you're using JS, Math.random() works. If PHP, rand() will work. Just use an if or case statement to check the value and display the ad accordingly.

 

i have a blog on the blogspot
i puted my js file on the google pages ...
(pages.google.com)

 

plz give me a full js file(an exam)