Basically for fonts to look good when placed on a square grid (pixels) there is a method called hinting which as the name implies gives hints to the font renderer on how the fonts should be drawn across this grid in order to best preserve the intended look of the font and be readable, this has the greatest impact when you are using a very limited size grid such as in small font sizes.
Basically for fonts to look good when placed on a square grid (pixels) there is a method called hinting which as the name implies gives hints to the font renderer on how the fonts should be drawn across this grid in order to best preserve the intended look of the font and be readable, this has the greatest impact when you are using a very limited size grid such as in small font sizes.