Authenticating thru Active Directory

I’m trying to create a log in page that authenticates thru Active Directory

[Stoneman7]

Here’s my situation:

When the user submits their credentials, they authenticate thru AD and sends them to the Default.aspx page where they greeted a dropdownlist users that are in the same OU as the logged on user.
I guess question is, how can go about doing this?

Thank you for the help.

[carguy84]

Can't do it in javascript, it's going to require server side programming.