The compose window in Google Mail is traditionally locked to the bottom of your screen. This works fine most of the time, but there are some instances when in would be beneficial to have a compose window that you can move around so you can minimize your browser. There is a very simple way to make this happen.
All you need to do in order to have a movable compose window is to hold down the shift key while you are clicking compose with your mouse....Tada! Movable compose window.