EXAMPLE TEXT:

Internet Explorer (6,7,8) can mangle your
anti-aliasing when the ActiveX opacity filter
is applied to a floating object like this.

EXAMPLE IMAGE:


(note: screen cap was taken in IE 6 on Windows XP with "ClearType" anti-aliasing mode in effect. Results will vary by system.)

DANGEROUS CSS COMBINATION:

  float:left;
  filter:alpha(opacity=100);
* Note that if any alpha is defined (100 is just an example), it will trigger error.

SOLUTION:

It turns out that IE is confused about which background color it should anti alias against. Seems to choose black in this case. If we explicitly define a background-color, the rendering issue goes away.