This Stack Overflow icon is made in Material Design style developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 5,500 icons, all in the same style and quality.
Idea of Stack Overflow Icon by Robert
We've received the idea on February 09, 2012 and created the icons on April 18, 2012
Stackoverflow.com Logo. It would be awesome if you could style the favicon from http://stackoverflow.com/ like the GitHub Icon