You want to write a div into your HTML that contains your login fields (i.e. the popup window). Set it to position:absolute;
and position with CSS so it floats above the page contents and doesn t interrupt the flow when it appears. Get it all nice and positioned where you want it, then set it to display: none;
so it will wait for javascript to make it appear.
Then (using jQuery), write something like this:
$( #register ).click(function() {
$( #popup ).show();
});
where #register
is whatever gets clicked (can be most anything with id="register"
).
What happens whenever that form is submitted is up to you, and not any different from the options you d have with any other HTML form. jQuery can help with AJAX if you decide to go that route and not send the surfer to another page to process the form.