How does one create a Pop Up window where the window that pops up is not
a Web browser via the Javascript Open command but the window that opens
up is a custom window but it is still HTML.

To see what I mean for example go to:
and click on the Log-in link that is on the top right corner. Once you do then a small window pops up where you can enter your userrname & password. This is the type of a pop up window that I need to create.

Also please do not suggest JQuery as the solution, but the actual Javascript and other code.