Works fine on my Win7, so the link is probably ok.

The midi opens in Windows Media player on mine, so perhaps you've not got it set to play .mid(?) or you're using something else for your player that needs a tweak.

First thing I'd check would be whether a .mid file opens and plays from your own machine, to see if it's a local problem or something with your browser. If local files play okay, a popup blocker would be the next suspect. Default "security" settings in Win7 can be a bit obscure, and some add-on "defenses" can be downright weird.

John