I noticed that Safari desktop and Webkit do not play VBR (variable bitrate) MP3 files. I tried using HTML5 embedding and I also just pointed the browsers directly to the MP3 files and they will not play. both mobile Safari and Chrome play VBR MP3 files fine. this is not an issue with constant bitrate MP3 files. here is a direct link to a VBR MP3 that plays perfectly in Quicktime, iTunes, mobile Safari, and Chrome, but not in desktop Safari and Webkit: http://www.mediastream247.com/audio/test/s/01.mp3
Thanks very much for the bug report! This is a bug in the underlying media framework on Mac OS X and not in WebKit, so this report needs to be filed at http://bugreport.apple.com instead of here.