在做oauth时如何创建弹出窗口？

I'm would like to do what lifestream and other sites have done with oauth authentication by using a pop up window. They open a popup window which somehow wasn't blocked by the popup blocker and grey out their site. Then upon allowing oauth access it says redirecting back to original site and kills the popup and returns the site to normal color. How would I go about doing something like this? If I posted anything I shouldn't have its alright because all these accounts are bogus anyway.I'm would like to do what lifestream and other