关键词：clear: both; display: block; margin:auto;
图片居左，居右，居中：
/* Alignment */
.alignleft {
display: inline;
float: left;
}
.alignright {
display: inline;
float: right;
}
.aligncenter {
clear: both;
display: block;
margin:auto;
}
连接：http://www.jb51.net/css/134690.html