.clearfix{display:block;clear:both;float:none}body{display:block;margin:0;padding:0;font-family:roboto,sans-serif;}nav{display:block;background:#f2f2f2;padding:20px}nav h2{display:block;float:left;color:#2b2b2b;text-decoration:none;margin:0;padding:0}nav ul{display:block;float:right;list-style:none;margin:0;padding:0;margin-top:5px}nav ul li{display:block;float:left;margin-left:20px}nav ul li a{color:#5ba9e2;text-decoration:none}nav ul li a:hover{text-decoration:underline}.video-back{display:block;padding:23rem 0;text-align:center}.video-back h1{display:block;text-align:center;color:#fff;font-size:50px}.video-back p{display:block;color:#fff;margin:0;padding:0;margin-bottom:20px}.video-back img{width:150px}.main-heading{text-align:center;margin:50px auto;font-size:70px}.main-para{margin:10px 100px;text-align:center;font-size:20px}.jq22-demo a{color:#f0f8ff;font-family:微软雅黑;font-size:20px;text-decoration:none;padding-left:10px;padding-right:10px;font-weight:700;text-shadow:2px 2px 4px #000}