Here’s a quick tip about the Aqua interface windowing system that you may not be aware of.

Every application and document window in OS X has the three red, orange and green buttons, or what I like to call the ‘traffic light’ buttons in the left of the window’s title bar. The buttons close, minimise, and toggle the window’s standard size respectively.

Another cool thing is that close button displays a dot if the window contains unsaved work. The title bar’s proxy icon (immediately before the window title) is also dimmed to show that the document has unsaved changes. This means if you are working on several documents like email or Word files, you can easily tell which ones you have saved and which you have not by the traffic lights and how the title bar displays the icon.

Now you know

Find out more about window appearances in OS X’s Aqua Interface in Apple’s Human Interface Guidelines.