popup window for restricted accessing part of site

I´ve been looking all over the place for some kind of code that helps me make part of my web accessible only with a password and username. I´ve seen it working in many sites.I´d like it to do something like this:
when u press the link a popup box appears asking for username and passwrd, if theese are correct, a page is opened were you get the user restricted area.
I´m sorry if it´s a silly question but i´m only a newbie
Thank you in advance for your help!

Depends what type of machine you are hosted on NT or unix. But the result is the same.
You do many different things.

For unix ..

Best is to password protect a certain directory and place the files you want to protect here. Then create a .htaccess file and place it in the directory. Create a password for username in .htaccess file.
Bang your directory is protected.

You'll need to get on to your host basically.
Commands for above operatations can't be found in any search.

Also can do a javascript username and password thing but ppl just have to look at the source for that.
Also you database can hold the password, ask by code.

Hope this helps some way.

--cj