Don't use pop-ups. Seriously. They're broken. Intentionally broken. Too many people misused them, and so we had to break them. They're not gonna get less broken either, 'cause folks would just misuse them again. But, ignoring that, assuming they did work reliably, you still wouldn't want to do that. Because now, you've locked the user's browser window, with all the nice friendly browser-window controls they've become so accustom to, and forced them to deal with your little dialog. Here's a better idea: if you don't need or want them to see or interact with the page contents, then redirect them to another page and put your dialog stuff on it. If you do want or need them to see (but not interact) with the page contents, then use one of the many "lightbox"-style dialog techniques available to overlay the page with a semi-transparent layer on top of which you can place your dialog stuff (but still all contained within the page itself). And whatever you do, don't forget to make the Escape and Enter keys work sensibly. If it looks like a dialog, then make it act like one.
But who is the king of all of these folks?