Many of them require GS extensions to work as supposed. Some of them will play fine with simple GS extansions, but a few of them requires advanced GS extansions for special effects, instruments or ethnic percussions.

For people who use Windows, a GS softsynth comes with the OS, but it lacks any reverb and effects, and only have basic GS extensions. Because it lacks the "GM fallback" system, any attempt from me to use further GS extensions will sound like silence (instead of the corresponing GM instrument), making things even worse. It's definitely not suited to play most of my MIDIs. (I don't know if there is a default softsynth on Linux and Mac OS).

Is it fine with this site ?

I haven't had any problems with the MIDI's you submitted. They all sounded great. I know that I use Quicktime to play MIDI's on my computer and have had no problems at all. They should be fine with this site.

They sound alright on my comp, too. If I notice anything funny with any of the MIDIs I'll drop you a note, Bregalad.