clear:both
使元素放在文档中其前面的任何浮动元素的下方.
也可以使用clear:left
或clear:right
使其仅低于那些已向左或向右浮动的元素.
+------------+ +--------------------+
| | | |
| float:left | | without clear |
| | | |
| | +--------------------+
| | +--------------------+
| | | |
| | | with clear:right |
| | | (no effect here, |
| | | as there is no |
| | | float:right |
| | | element) |
| | | |
| | +--------------------+
| |
+------------+
+---------------------+
| |
| with clear:left |
| or clear:both |
| |
+---------------------+