Previously, users could use window.createPopup() to open multiple windows per page. SP2 stops this.

Everybody knows the sites. You go looking for coolie information and find yourself at a porn or warez site by accident. You try to leave, and you get bombarded with multiple pop-up windows. Click, click, click — you cannot close them fast enough before more are created.

Frequently, this was abuse of the window.createPopup() method for creating a new window. Because of this abuse, Windows will no longer allow more than one pop-up window per page.

This will trouble some web designers that have legetiment reasons to use multiple pop-up windows.

In the world of SP2, this will no longer be acceptable.