One thing that I absolutely hate is a webpage that starts playing music when I navigate to it. This is one (of several) reasons that I avoid My Space pages like the plague. Haineault.com has a great post on this very issue.

He gives a few reasons that you should not have autostarting music on your webpage. My two favorites are:

• your music choice most likely sucks, if not, it will be outdated soon enough.
• if your visitors want to listen music they will listen their mp3, your site is not a jukebox. In fact they most likely already are listening music and yours is only mixing with it, creating an unbearable and unwanted musical chaos.

If this too drives you crazy, I recommend an extension for Firefox called Flashblock, which blocks all flash media from loading. You can then manually start the flash items. You can also white list certain pages so that the embedded flash works normally.