I am doing this for a couple of reasons:
1) It will make it harder for someone on the net, such as your ISP, to see what you are doing here or sniff out your cookies or password.
2) It will hide, to the casual observer (such as your network administrator at work) the actual site you are visting.
This change will NOT make you anonymous. It will NOT hide what you are doing here from anyone who is visiting the site. It is purely here to encrypt the information as it flows from your browser to the server and vice versa.
The administrator may have required you to register before you can view this page.