That's because at those small sizes, there are not enough pixels left to render all those details. In this case rendering them would make the characters much too wide.
TrueType fonts have a system called hinting which aligns the outlines to the pixels of a screen. Since we can't make those characters wider than 1 pixel at those small sizes, we have to make them rectangular like that. The other option would be gray rectangles. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]

