I've had a couple of drinks. Bonnie's out for the night, and I'm in the mood to preach. Hit the back button unless you have some free time. This, quite likely, has litte or nothing to do with the orignal question, but I'm inspired.It would seem natural to use popups for help and explanation on web sites. Why don't you see it more?
I know this because I began my Web career working on a multimillion dollar failed project, and my task on the project was to implement popup help on all words (in this huge healthcare site -- lots of arcane Latin) that folks might not understand.
The problem is that popups fall behind the main window whenever you click on the main window. Lots of users don't understand why or how to get the window back. I recall dreading usability tests because I knew this would be a problem. It's cool to sit behind a two-way mirror watching folks use your site until you're work starts failing on the other side of the mirror. I was told to solve this problem. I said "no problem." Many have said "no problem" in similar situations, and still you do not see popup help on many if any sites.
The only way to keep a window on top when the user shifts focus to another window is to restore focus on that event. This is the rub. Even though you can put a button on the popup window that allows the user to close it, users often (according to tests I saw, it would seem always) don't see it. They completely freak out when they click off of the window and the window not only stays there. It prevents the user from doing anything on the main window.
You either offend the folks who don't notice the "close window" button, or you offend the folks who accidentally click on the main window and can't bring the popup back.
Many a web developer, myself included, has been scoffed at by his or her boss or client for not finding a third option.
I believe that I have more experience with popups than most folks you might bump into. It's not just that project. I once had to implement a brilliant desiger's vision of a site where all links were to precisely sized popup windows that scrolled sideways -- not vertically. It was by far the gooviest and coolest project I have ever worked on. The problem was that only the designer and I could navigate the site. I wish I had saved that project just to show you how incredibly cool an unexpected a Web site could be. Many of you would wonder why anyone would have any trouble with it. But that's because you understand the basic mechanism behind popup windows and because you've been warned. You must understand how popups work in order to not hate them as a web surfer, and then you still probably hate them.
I once used a popup window on my home page to try to boost subscriptions to OutFront News. It did that, but I finally got around to testing my site on a friend's machine who uses AOL. The window popped up at full screen size completely covering the main window even though my cross-browser-compatible script controlled the window size. I wasn't so upset about how ugly it was, but I was amazed that I hadn't fielded more complaints from aol users about such a way blatant attempt to force folks to subscribe to my NL.
I was horrified to see that my script was not controlling the window size for aol users. AOL is the big enchilada. I decided then and there that I would never do another cool web trick without testing it on aol. Since I just can't stand to wait for aol to load, that means I just don't do cool web tricks anymore.
I probably would never have gotten into this industry had I believed at the outset what I have come to believe since. The most effective thing on the Net is a compilation of simple static Web pages containing quality information hyperlinked to other simple static Web pages containing quality information.
This is a lot to read through. I bet I'm just writing to myself right now. I would be overjoyed to learn otherwise. Absolut Peppar on the rocks is not for everyone, but neither is OutFront.