Styling the Default Audio Player

I have a basic audio player using the standard default [audio] shortcode on this page. I don’t know why, but the audio player is extending way far to the right, even wider than the rest of the page is.

I tried to put a div around it, and styled the div:

#audio {
max-width:500px;
background-color:#a01e0c;
height: 45px;

}

I can see this div working but it isn’t containing the width of the audio player.

How do I fix this? Or more simply, how might I style the audio player?

The page I need help with: [log in to see the link]