I've been using blogger for a while, and not because I don't know how to build my own blog or website. I've build dozens of them, but I use blogger because its easy, and I don't have to worry about the details of the code. Heck I could build a site like blogger if I wanted, it would just take time. Occasionally on blogger I bump into a feature that I don't know how to replicate, and this is one of them.
I was browsing around in some MSDN DOM documentation and found a window event called onbeforeunload. I've actually explored this issue once before and only got as far as onunload. Having the right keyword to put into google makes a real difference.
source(s): http://msdn2.microsoft.com/en-us/library/ms536907.aspx, http://www.4guysfromrolla.com/demos/OnBeforeUnloadDemo1.htm