放在<form>里面
<form>
<asp:TextBox id="txtUserName" style="Z-INDEX: 103; LEFT: 58px; POSITION: absolute; TOP: 29px" Width="79px" Height="19px" runat="server"></asp:TextBox>
</form>
<form>
<asp:TextBox id="txtUserName" style="Z-INDEX: 103; LEFT: 58px; POSITION: absolute; TOP: 29px" Width="79px" Height="19px" runat="server"></asp:TextBox>
</form>
服务端控件必须放在 runat=server的form里面!