在页面顶部我已经注册了，但还是报错，求指导
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="index.aspx.cs" Inherits="index" %>
<%@ Register Src="~/enter.ascx" TagName="enter" TagPrefix="uc1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<uc1:enter id="head1" runat="server"></uc1:enter>
<form id="form1" runat="server">
<div>
</div>
</form>
</body>
</html>