Code:
<&#37;@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<!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>Untitled Page</title>

    <script language="javascript" type="text/javascript">
    function validate()
    {
    if(document.getElementById('TextBox1').value=="" && document.getElementById('TextBox2').value=="")
    {
    alert("Please enter the UserId and Password");
    return false;
    }
    else if(document.getElementById('TextBox1').value=="")
    {
    alert("Please enter the UserId");
    return false;
    }
    else if(document.getElementById('TextBox2').value=="")
    {
    alert("Please enter the Password");
    return false;
    }
    else
    {
    return true;
    }
    }
    </script>

</head>
<body>
    <form id="form1" runat="server">
        <div>
            <asp:Label ID="Label1" runat="server" Text="UserId :"></asp:Label>
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <br />
            <asp:Label ID="Label2" runat="server" Text="Password :"></asp:Label>
            <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="Button1" runat="server" Text="Submit" OnClientClick="return validate()" />
        </div>
    </form>
</body>
</html>
please have a look at this code........is it ok