They are using Apache for their webserver.

I once had occasion to run some PHP software and not having access to a Linux box, I installed Apache on my WinServer.

Surprising how many of the big sites are running IIS these days though.

Eric, if you want to see who all are doing this, notice the addresses that contain either an ASP or ASPX somewhere in the address bar. Maybe there is a solution for the Linux crowd that wants to do this, but I haven't found one - been a couple years since I've looked though.