Ive added a sound file to this page:
http://mgrover.coffeecup.com/Twinhorns.html
However it doesnt appear to be working, Ive uploaded the .wav file, and hopefully inserted the correct code onto the page, can anyone advise me on this problem.

The script is pointing to this.
http://mgrover.coffeecup.com/horn.wav
It needs to point here.
http://mgrover.coffeecup.com/sounds/horn.wav

Your sound file, "horn.wav" (is this really what I think it is?), does not seem to be present in the root directory, where it is expected by your script.

This is probably just as well, though, since an auto-starting sound of a car horn could be a pretty horrible experience for your unsuspecting visitors, especially if the volume happens to be set high...
I think most people find auto-starting sounds on websites quite irritating, even if it's not a car horn.

Think maybe its not a very good idea after all.