HiddenField Name mangling

Hi all,
 
Another newbie question.  I'm attempting to post form data to a third party website.  My problem appears to be that ASP is mangling the names of my input elements.  For example, if I use:
 <asp:HiddenField ID="cmd" Value="_cart" runat="server" />
OR
<input ID="cmd" Name="cmd" Value="_cart" type="hidden />
what I end up with in the source is:
<input name="ctl00$MainContent$cmd" type="hidden" id="ctl00_MainContent_cmd" value="_cart" />
As you can see, the ID and name have been mangled.  It appears that the mangled name is what is being sent to the third party website and of course it is expecting "cmd", NOT "ctl00$MainContent$cmd".  The result is that the third party site does not react properly to my request.
 I've tried a test page t ...