Coloring Every Other Line in PRE

line-height: 18px;
background-image: linear-gradient(
  top,
  rgb(255, 255, 255)    0,
  rgb(255, 255, 255) 18px,
  rgb(243, 246, 252) 18px,
  rgb(243, 246, 252) 36px
);
background-image: -moz-linear-gradient(
  top,
  rgb(255, 255, 255)    0,
  rgb(255, 255, 255) 18px,
  rgb(243, 246, 252) 18px,
  rgb(243, 246, 252) 36px
);
background-image: -webkit-gradient(
  linear,
  left top,
  left bottom,
  color-stop(  0, rgb(255, 255, 255)),
  color-stop(0.5, rgb(255, 255, 255)),
  color-stop(0.5, rgb(243, 246, 252)),
  color-stop(1.0, rgb(243, 246, 252))
);
background-repeat: repeat-y;
font-size: 12px;
-moz-background-size: 100% 36px;
-webkit-background-size: 100% 36px;

Requirements: Firefox 3.6 Beta 3+, Safari 4+ or Chrome 4+.