how to, un-install a free online browser game
I dunno because I don't really play downloaded games. But, I can offer that, if you use XP, you could try a "restore" to a previous time function (before you installed the game). Ok, free game sites usually make their money through advertising. If you are talking about pop-ups, etc., and other ads, you might be able to use an anti-spyware, malware program to identify and remove it. You should, btw, google your question using the specific game as a keyword. There are probably others with the same issue. You can look in "add remove programs" for anything suspicious, too. But, the problem might be in services that the program installs.
Somebody else might also be able to give you advice about setting up a safer enrionment -like Sandbox-- where you don't have to install programs to you disk/os. Good luck.
"A man is rich when he has time and freewill. How he chooses to invest both will determine the return on his investment."