h5bp clearfix
/*
* Clearfix: contain floats
*
* For modern browsers
* 1. The space content is one way to avoid an Opera bug when the
* `contenteditable` attribute is included anywhere else in the document.
* Otherwise it causes space to appear at the top and bottom of elements
* that receive the `clearfix` class.
* 2. The use of `table` rather than `block` is only necessary if using
* `:before` to contain the top-margins of child elements.
*/
.clearfix:before,
.clearfix:after {
content: " "; /* 1 */
display: table; /* 2 */
}
.clearfix:after {
clear: both;
}