Hi,
"<form action="enviarconsultaonline.php" method="post" name="frm" onsubmit="return valida(this)">"
In ASP.NET WebForms there can be one and only one form element on a page and one already exists so you cannot add another one.
If you need to do a custom form post you cannot do that using the html content feature, you would need to create a custom feature and use an <asp:Button
You can set the PostBackUrl on the button and this will make the alrerady existing form on the page post to the specified url.
See the articles:
Hope that helps,
Joe