H2 wierdness

Somehow, my CSS H2 declaration creates a huge gap above it. See, for example,

Content h1, Content h2, Content h3, Content h4, Content h5, Content h6 {
color: #000000;
line-height: 1.5em;
margin: 0 0 20px;

What am I missing?

That gap is not caused by the H2, but by #main which has padding: 40px 0 0;