I’ve seen some funky solutions to this problem, including using a hidden submit button which appears first in the form, but I’ve found the following works fine – change all the submit buttons that you don’t want to be default to normal buttons, i.e., type="button" instead of type="submit", and use their onclick events to submit the form. For example:

<form id="myform" method="get">
<!-- Not the default button -->
<input name="b1" type="button" onclick="this.form.submit()" value="B1" />
<!-- The default button -->
<input name="b2" type="submit" value="B2" />
</form>

1. Make a sweet little 16×16 PNG favicon in your favorite paint application
2. Butcher it into an ICO file using favicon.cc
3. Upload both files to your web server
4. Stick the following code in the HEAD section of your webpage

<link rel="icon" type="image/png" href="favicon.png" />
<!--[if IE]>
	<link rel="shortcut icon" type="image/x-icon" href="favicon.ico" />
<![endif]-->

5. Reassure yourself that IE users are pretty used to a sub-standard web browsing experience, and won’t be bothered by the lack of proper transparency or 24bit color in the favicon they see