Window popups - how to get window.blur() or window.focus() to work in FireFox 4?

I'm aware that FF4 doesn't allow the use of window.blur() unless "Raise or lower window" setting is enabled in the FF configuration. It simple ignores the event.

I'm aware that some site still manage to open a pop-up window and keep focus on your current window, even when this setting is switched off. How do they achieve this?

Additionally, I don't understand why .blur() and .focus() doesn't work when both pages reside on the same domain. According to http://support.mozilla.com/en-US/questions/806756#answer-167267 this should work.