Tracking

Kerning fixes one pair; tracking moves them all. It is a blunt instrument and it has two honest uses. Large type usually needs a little taken out, because spacing drawn to work at sixteen pixels looks loose at sixty. Small type, capitals and light weights on dark grounds usually need a little added, because in each case the letters are closer together than they appear to be.

The values that work are much smaller than people expect. In CSS, a headline rarely wants more than -0.02em and a line of small capitals rarely more than 0.08em; anything past that stops being typography and becomes an effect. Negative tracking on body text is almost always a mistake — it closes up the word spaces along with everything else, and the words stop being separate objects.