I’ll do what I can to get the size limit increased a bit, but generally, a full song at 160kbps is an easy fit, and you can often get away with 192kbps.

The real trick is to make sure you normalize your audio file before you transcode to MP3, this gives the encoding the best signal to work with, and can make transcoding artifacts close to inaudible.

There is some really good cheap and free software out there these days that make it easy to master your audio a little bit before you post, a tiny bit of multi-band soft compression, no more than 1 or 2 dB, and perhaps 2-3dB of limiting can do wonders to make a web file pop a bit from the speakers… do all this BEFORE you convert to an MP3 (most of these softwares have the option to export as an MP3 after you do a tad of mastering) and you give your file the best chance it can to take as little room as is available but still sound good…