I recently had a problem where I was opening a browser window from an e-mail client. After taking a survey, I wanted a button to close this same window. In IE, it was fine to simply use window.close(); to close the window. However, Firefox, the evil genius that it is, will not let you do that because it believes you did not click to open this window in the first place. In order to trick it, you quick load a blank page then close it. The code:
Close this window</a>
So now, when you click the link, it closes the browser window. It works in both IE and Firefox 1.5 (and I believe others as well, but not personally tested). Finding that snippet of code saved me a lot of time! So I hope someone else finds it useful.
Update, May 1 2008:
This code only works on Firefox 1.5 and IE. In Firefox 2.0, Unless a website opened up a window – it can not close it. So, in my case I want to close the window after a user takes a survey, opened from an email window. Firefox 2.0 gives this error: Scripts may not close windows that were not opened by the script. I’m not sure what the right answer is here. They are doing it to prevent malicious scripts from closing windows. But even if they added an option to change that, most users wouldnt have it enabled by default.