Are you trying to make your own music and post an MP3? More than likely what you have now itsnt an MP3 file to begin with. What program are you using? Audicity can convert files into MP3's. Most files are WAV. and MIDI files. Those arnt MP3's and can only play if your player accepts those files. Most of the programs you use have their own file. Like reason, cubase and such. If you buy the full versions you can convert the files or "export" them as MP3 files. Once you get an MP3 on your hands and you want to use a FREE hosting site, try
SOUNDCLICK but, it'll only upload MP3's. There are certain programs you can download for free to do MP3 conversions. Here is a link to another message board's thread for free software and MP3 junk:
If your budget is $0.00Hope that helps. If you have any questions you can PM me.