Agregá esto al final de tu style.css
Código:
.center {text-align: center;}
img.center, img[align="center"] {display: block;margin-left: auto;margin-right: auto;}
.alignleft {float: left;}
img.alignleft, img[align="left"] {float:left;margin: 2px 10px 5px 0px;}
.alignright {float: right;}
img.alignright, img[align="right"] {float:right;margin: 2px 0px 5px 10px;}
.clear {clear:both;}