Popup window

[Comograma]

Is it possible, by clicking a button, open a popup window (modal window) which the content of that popup is a external page (external link)?

See this example:

https://github.com/Atozed/IntraWeb/tree/...odalWindow

Thanks!! I'd try the example but when I hit button "Show another site", passing my site link do the function ShowSite(), like this:
ShowSite('This is Atozed''s Blog', 'https://www.comograma.pt');

nothing is shown, I get an empty window. See attachement. Why is that happening?