Authentication Required!

I have a website which is basically done for now: Click Here . What I want to do is whenever you go to it, it will have a popup box REQUIRING a username and password. The username and password will be universal, like user: admin, pass: password, so its not like you can register an account. I don't need top of the line security like having the username and password encrypted. If you successfully provide the correct credentials, it will let you continue, if not you keep on guessing. If possible I would like it to save that you have been validated and you don't need to re-login on any other page on the site. No matter what page you are on, even if you go directly to a certain page, the website should require a login. Note: If possible, can you make it save that you correctly logged in for like 5 minutes or something.

The only languages I really am interested in this being in is HTML, & Javascript. Some Panel's have features like password protecting but I can't find one for this site.
I believe what I am looking for is an HTTP authentication, but I don't know.

Thanks...