error correction for my html code

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C#

ASP.NET

HTML

Hai,
I downloaded a template and tried to edit that template using visual studio.While trying to edit its contact page, I replaced its textbox and button with that of toolbox textbox and buttons.But it did'nt create the textbox instead displayed error showing "error creating control value cannot be null parameter name:frameworkname".which value does this error refer to.it would be kindful of you if you could help me correct this error.Following is the html code

<div id="templatemo_main">
	
    <h2>Contact Information</h2>
        <div class="half float_l">
        <h4>Send us a message now!</h4>
            <p>If you have any query,Please let us know</p>
            <div id="contact_form">
            	Name:<asp:TextBox ID="Txtname" runat="server" Width="398"></asp:TextBox>
            	<br />
 Your Email:<br />
 <asp:TextBox ID="txtmail" runat="server" Width="398"></asp:TextBox>
 <br />
 Subject:<br />
 <asp:TextBox ID="txtsubject" runat="server" Width="398"></asp:TextBox>
 <br />
 Message:<br />
 <asp:TextBox ID="Txtmsge" runat="server" Width="398" Height="200" TextMode="MultiLine"></asp:TextBox>
 <br />
 <asp:Button ID="Btn" runat="server" Text="Send" />
            	</div>
		</div>