<input type="submit" name="Submit" value="Submit" id="Submit" />

<form id="form1" runat="server">
<div>
    <asp:TextBox ID="txtTest" runat="server" />
    <asp:Button ID="Submit" runat="server" Text="Submit" />
</div>
</form>

<input type="button" name="submit" onclick="this.form.submit();" value="try" />

<form id="form1" runat="server" onsubmit="this.submit()">
<div>
    <asp:TextBox ID="txtTest" runat="server" />
    <asp:Button ID="Submit" runat="server" Text="Submit" Type="submit"/>
</div>
</form>