Based on Markup

You can load popup completely from a markup. It will read title, body, buttons, as well as width and height of the new popup content. See example below how it works. The div that contains markup should have style="display: none", so it would not be visible on the page, if you include it into the same page.
Use rel=title, rel=body, rel=buttons to defined popup parts and style="width: XXpx; height: XXpx; overflow: AA;" of the initial div to define size and overflow. outside of the popup will close it.