Selenium: Testing pop-up windows
For the Selenium RC API, you need to use the SelectWindow command to switch to the pop-up window.  The window can be specified either by its name (as specified on the JavaScript window.open() function) or its title.  To switch back to the main window, use SelectWindow(None).
I have an issue when trying to test a web application with Selenium/Python. Basically I can't test elements of a pop-up window. 
A scenario: I can test all elements for a page. But when I go to click on a button that opens up a small pop up box I can't test the elements on the popup. It's like the pop up isn't in focus or active. 
I can test elements on the next page. For example click a button, brings me on to next page, and I can work with elements on the 'next' page. So it the problem seems to be popup specific.
I could post code but to be honest it might confuse at this stage. I may post code in a later post, thanks