masterpage, form and action

 i have a masterpage file, 1 page is sample.aspx.
in sample.aspx, i have form tag which set runat ="server".
but i can't add action into this form.
 












<form id="form1" action="https://www.paypal.com/cgi-bin/webscr" method="post">
                        <input name="cmd" value="_xclick" type="hidden">
                        
                        <asp:literal id="litem_name" runat="server"></asp:literal>
          &nbs ...