different ads on dif browsers?

How come firefox and IE displays different ads on the same sites? By different i mean COMPLETELY different, like different types of ads.

 

e.g?

tell me any site that shows different ads on both browsers

 

I guess it depends on the site, because I rarely see a lot of variations between the ads across browsers.

 

I guess google use cookies to do all kinds of tracking and change ads targeting users of diff browsers.

 

I would have thought they would all be the ssame. Different browsers are set up to show the same content on a given page.

 

Site owner can add detection code to detect the browser and serve different type of ads for different browser users.
Some even detect if you have javascript disabled and if so they put you yet another type of ad.

 

I was thinking from a default status.

 

ex. you can detect if a user is using IE and then display a firefox referral button