design:
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="login.aspx.cs" Inherits="INSERT_UPDATE_DELETE.login" %>
<!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 id="Head1" runat="server">
<title>Untitled Page</title>
<script src="../validation.js" type="text/javascript"></script>
</head>
<body>
<form id="form1" runat="server">
<div>
<table align="center">
<tr>
<td>
USERNAME
</td>
<td>
<asp:TextBox ID="TextBox1" runat="server" Height="24px" Width="133px"></asp:TextBox>
</td>
</tr>
<tr>
<td>
PASSWORD
</td>
<td>
<asp:TextBox ID="TextBox2" runat="server" Height="22px" Width="133px"></asp:TextBox>
</td>
</tr>
<tr>
<td>
</td>
<td>
<asp:Button ID="btnSave" runat="server" Text="Insert" OnClick="btnSave_Click" OnClientClick="return isvaliduser();" />
</td>
</tr>
</table>
</div>
</form>
</body>
</html>
validation.js
function isvaliduser() {
if (document.getElementById("<%=TextBox1.ClientID%>").value == "") {
alert("Name cannot be blank");
document.getElementById("<%=TextBox1.ClientID%>").focus();
return (false);
}
}