Mozilla Question...
 

Does Mozilla / Firefox handle url referral?

What do you mean exactly? Redirects? HTTP_REFERER?

Some sites use what's called url referral to gain access to protected areas. A lot of the plug in feeds use this system. The broswer must be able to pass on the URL that the surfer came from, and it's matched against a list. If the URL is an approved URL, access is granted. If it's not, the surfer is rejected.

Does Mozilla / Firefox use this?

Sure these browsers support it.

However, I think that it can be disabled in Firefox (user can disable the browser from sending referrer info). Not sure about it, but the user

Stupid 1-minute edit feature lol