Multiple Contact Forms Within A .NET Page?

Tearing my hair out here trying to implement a pretty simple form inside a .NET page.

The form looks like this:

<form action="http://domain.com/subscribe.tml" method="POST">
<p><input name="email" type="text" /></p>
<p><input type="image" src="/images/ui/btn-getfreereport.gif" alt="Signup" /> </p>
<input type="hidden" value="one_hello" name="confirm" />
<input type="hidden" value="F" name="showconfirm" />
</form>

Leaving the plain <form> code in there actually seems to work, except for in IE, where it adds a ~200px margin underneath the </form> (and using CSS to remove the margin and padding doesn't help).

I read about the HtmlForm class, but can't find examples of how to send data for the form above.