#boite
{
	width: 200px;
	height: 200px;
	border: 2px solid #000;
	background-color: red;
	margin-left: 200px;
	transition: margin-left 2s;
	-moz-transition: margin-left 2s;
	-webkit-transition: margin-left 2s;
	-o-transition: margin-left 2s;
}

#boite:hover
{
	margin-left: 300px;
}