右击查看源代码

.div{
	width: 300px;
	height: 300px;
	background: red;
	-webkit-transition: all .5s ease-in;
	-moz-transition: all .5s ease-in;
	-ms-transition: all .5s ease-in;
	-o-transition: all .5s ease-in;
	transition: all .5s ease-in;
}
.div:hover{
	width: 500px;
	background: green;
}