You know the green dot on the upper left of all OS X windows? This one: 
.
I have no clue what it does. I’ve even been afraid to hit it 99% of the time because I have no idea what it’s going to do. I just clicked it for one of my Firefox windows and look what happened:
For all the good things that OS X does well, there’s still so many that it does wrong (see the ironically named “Finder”).
That’s the “Zoom” button. It’s suppose to re-size the window.
The full low down on how developer should apply zooming is here:
http://developer.apple.com/documentation/UserExperience/Conceptual/AppleHIGuidelines/XHIGWindows/chapter_18_section_5.html#//apple_ref/doc/uid/20000961-BACEDHFG
“user can toggle between the standard state and the user state by clicking the zoom button. When the user clicks the zoom button of a window in the user state, your application should first determine the appropriate size of the standard state. Move the window as little as possible to make it the standard size, and keep the entire window on the screen. The zoom button should not cause the window to fill the entire screen unless that was the last state the user set.”
Apple lies then! It goes to the mini player in iTunes which breaks their guidelines.
eh? I think iTunes follows the toggle between the standard state (i.e. Catalog / CoverFlow) and the user state (mini player) model…