title: CSS: Circle with four colors and only one div
body: <p>Is it possible to create a circle with four different colors (one for each quarter) using pure CSS?
  I want something like one of these four circles:</p>
  
  <p>[Unfortunately the image I linked to does not exist anymore. Please see the answers to understand the what effect I was after]</p>
  
  <p>I can imagine using a solution with four divs and border-radius, but is this possible using only one div and some fancy css3?</p>