Hi Miklos,
Generally speaking, Pop-ups can be classified in three following categories:
1. General browser pop-ups
2. Messenger Service Pop-ups
3. Adware||Spyware Pop-ups
General Browser pop-ups Internet Explorer
These are created using one of two methods, "window.open" method or the window.createPopup" method. The "window.open" method creates another Browser Window either as a Pop-up or Pop-under. Windows Popup Blocker and most third party Popup Blockers will prevent this type scripted Popup Window. Windows Popup Blocker does not block the "window.createPopup" method(this is a Cromeless popup window), however this method is restricted to one per page and since SP2 also has size restrictions by default.
Messenger Service Pop-ups
This type of Popup is applicable only to Windows 2000 and Windows XP. The "Messenger Service" [different from Windows Messenger IM] is responsible for transmitting these text-based Pop-up message. Windows XP SP2 turns off the Messenger Service by default, and enables the Windows firewall. This blocks the ports required for Messenger Service data transmission, thus preventing this type Popup.
Adware||Spyware Pop-ups
This third category of course is the reason we are all here in this forum. Adware||Spyware pop-ups have same effect as General Browser pop-ups but they are usually powered by malware Browser Helper Objects, ActiveX controls which attaches to Internet Explorer and contact the respective AD servers to fetch ADs through internet.
The quasi Popup at the site you posted the link for does not fit into any of these three categories of Pop-ups(as described above), that site appears to be using JavaScript to generate an Image map that overlays the content of the page. The only way I know of to prevent that type of abuse(assuming you find it abusive) is to disable active scripting in your Browser in the Internet zone...as I described in my earlier post for Internet Explorer and Firefox.
I don't assume to be an expert in these matters Miklos, but this is the best way I know(in general terms) to answer your question.
Good luck,
Donald Anadell