interesting volume problem

[mrhnau]

I'm running into an interesting issue... I've got my volume muted, but periodically, I run across sites that will still come across with audio. I don't want to turn my speakers off, because periodically I actually want to hear something, but I'm quite tired of noises popping up when I don't want them. Any clues why this is happening, and what I can do to fix it? I'm running WinXP at the moment and I've got "mute all" selected on the volume control.