Login Session

i hav e created a simple user login page see below. But i would like to have a greeting like hello then username. But if you look at how i have done it below the Hello always stays on the page. is there away to get the hello to appear only when someone is logged in??
Code:
<Form Method=Post Action="welcome.asp">
UserName: <input Type=Text Name="Username">

Password: <Input Type=Password Name="Password">
<input Type=Submit>
</form>
<a href="userregistration.asp" class="links">Register</a>
<a href="Logout.asp" class="links">Logout</a><br />

<%
Dim strUsername
strUsername = Session("Username")
Response.write "Hello " & strUsername & ""%>