HTML元素margin、padding的默认值
| element | margin(单位像素) | padding |
| html | 0 | 0 |
| body | 8 | 0 |
| div | 0 | 0 |
| h1 | 21 | 0 |
| h2 | 19 0 19 0 | 0 |
| h3 | 18 0 18 0 | 0 |
| p | 16 0 16 0 | 0 |
| ul | 16 0 16 0 | 0 0 0 40 |
| li | 0 | 0 |
| td | 0 | 1 |
| dl | 16 0 16 0 | 0 |
| dt | 0 | 0 |
| dd | 0 0 0 40 | 0 |
body,h1,h2,h3,h4,h5,h6,p,ul,dl,dd{margin:0;padding:0}
