css3过渡属性结合jq，如果直接复制代码运行，需要加载一个jquery文件
<!DOCTYPE html PUBLIC -//W3C//DTD XHTML 1.0 Transitional//EN http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd>
<html xmlns=http://www.w3.org/1999/xhtml>
<head>
<meta http-equiv=Content-Type content=text/html; charset=utf-8 />
<title>m</title>
