Today i found a site http://www.hotfirefox.info OR http://www.freefirefoxdownloadsite.com/ Code (markup): which says download firefox and the site contains that page only are this kind allowed
Yes. Publishers are allowed to endorse the referral products, but must not encourage clicks on other ad formats. Read here for more information on referral endorsement.
Look at the TOS. Yes, it is allowed for the refferal items. They don't mind you saying for them to download the refferal things. They allow up to two of the same refferal things on a page.
Why not? As long as it has some content too. You could argue that these sites served as a review of FF as well as a download source.