I agree with Wullie. mailto: forms based in HTML are generally frowned upon, to be honest they are always frowned upon. If this is a business site or an organization, using this script will show the world your incapabilities.
I suggest you find a host which allows perl, asp, or php and grab one of their codes. It's a bit tougher, but better for the server, better for your email, and better for the guests.
This code is global, any system or browsers which allows HTML can display and use this page.
sulfericacid