Music online has to load from the server. By using a method called buffering it can play before the whole things is loaded (music files aren't a two second job to load), however if the buffering is slower than the song plays then the music will have to pause for a split-second every time it reaches the end of the buffered content, and wait for more to be buffered. The slower the connection the longer it takes to buffer, so it's more noticable if that's your case (It sounded fine to me).
I have broadband too, but the speed can vary greatly between each service. Mine isn't even that fast, to be honest. It's long-range wireless because I live away from town.
Not much you can do about buffering hiccups, unfortunately, and it certainly is quite unrelated to CSS and HTML in any case. Nice music though.