how to call aspx.cs method when window is closed

Aug 7 2013 4:45 AM

hi.............I am opening a window in asp.net as( window.open('ChatWindow.aspx', '_blank', 'top=610, left=1150,width=220,height=450,titlebar:no,toolbar:no,statusbar:no'))

as we know that it has minimize,maximize and close(X mark)....when close(x mark) is clicked how can i call code behind method...pls suggest me clearly....i tried with window.close()...it is not working