There’s been a sudden change-over in the past few years regarding UI design, including both icons/logos and total site design. Such changes are most noticeable in the Firefox and Chrome logos, which have gone from a more three dimensional look, to a very flat and mono-colored design, something that is supposed to appear less distracting, and more minimalist. Here’s an article discussing the changes and the benefits and cons, check it out.

http://uxmag.com/articles/a-look-at-flat-design-and-why-its-significant