Webkit fails to render a 1px vertical red line in the following example: -webkit-linear-gradient(left, white 0%, white 10px, red 10px, red 11px, white 11px, white 100%); Instead, it renders solid white.
However, the following will generate a 4px-wide red line: -webkit-linear-gradient(left, white 0%, white 10px, red 10px, red 12px, white 12px, white 100%);
Seems to be working in head (Webkit r109280)