Why is it that I cannot play games when I go to sites with games?

How is it that some sites i go to for games know I have Fox Mozilla or Netscape but cannot detect IE 8 which I downloaded recently?These sites want a plug in but Netscape does not allow it.Active X for games is already enabled on my computer.The biggest[and an ironic joke] is that I saw games advertised on my Yahoo Messenger and clicked the ad. Some games I selected are a one hour trial download so I closed them.Why cant I play the selected games from Yahoo online?Should I stick to Lycos or Pogo etc?