利用CSS虛擬元素 ：before 和 ：after 可以在文檔前後插入內容而不改變文檔原有結構，再配合 box-shadow 可以實現很炫的效果,
下面就展示三個例子：
1、利用 :before 和 :after 添加背景，比如給一段文字前後打引號；
2、利用 :before, :after, box-shadow 實現3D陰影製作效果;
3、利用 :before, :after, box-shadow 實現照片疊加效果.
<!DOCTYPE html> <html> <head> <title>Pseudo Demo</title> <style> body{background-color:#ccd3d7;padding:40px;} h2{display:block;border-bottom:1px solid #ddd;padding:15px;} p.myquote{padding:1em;font-size:16px;margin:8px 1em;position:relative;color:blue;line-height:1.7em;} p.myquote:before,p.myquote:after{font-size:40px;position:absolute;padding:0;margin:0;color:green;} p.myquote:hover:before,p.myquote:hover:after{color:red;font-size:50px;} p.myquote:before{content:"“";left:0;left:-10px;} p.myquote:after{content:"”";padding-left:15px;bottom:4px;} .shbox{ background:#fff; padding:10px; width:90%; margin:40px auto; height:auto; margin:40px auto; } .sh-down-lr{position:relative;} .sh-down-lr:before,.sh-down-lr:after{ z-index: -1; position: absolute; content: ""; bottom: 15px; left: 10px; width: 50%; top: 80%; max-width:300px; background: #777; -webkit-box-shadow: 0 15px 10px #777; -moz-box-shadow: 0 15px 10px #777; box-shadow: 0 15px 10px #777; -webkit-transform: rotate(-3deg); -moz-transform: rotate(-3deg); -o-transform: rotate(-3deg); -ms-transform: rotate(-3deg); transform: rotate(-3deg); } .sh-down-lr:after{ -webkit-transform: rotate(3deg); -moz-transform: rotate(3deg); -o-transform: rotate(3deg); -ms-transform: rotate(3deg); transform: rotate(3deg); right:10px; left:auto; } .stackone { border: 6px solid #fff; width: 400px; height:225px; margin: 50px; position: relative; -webkit-box-shadow: 2px 2px 5px rgba(0,0,0,0.3); -moz-box-shadow: 2px 2px 5px rgba(0,0,0,0.3); box-shadow: 2px 2px 5px rgba(0,0,0,0.3); } .stackone img{width:100%;heigth:100%;} .stackone:before,.stackone:after { content: ""; width: 400px; height:225px; background: #aaa; border: 6px solid #fff; position:absolute; z-index:-1; top:0; left:-10px; -webkit-box-shadow: 2px 2px 5px rgba(0,0,0,0.3); -moz-box-shadow: 2px 2px 5px rgba(0,0,0,0.3); box-shadow: 2px 2px 5px rgba(0,0,0,0.3); -webkit-transform: rotate(-5deg); -moz-transform: rotate(-5deg); -o-transform: rotate(-5deg); -ms-transform: rotate(-5deg); transform: rotate(-5deg); } .stackone:after { top:5px; left:0; -webkit-transform: rotate(3deg); -moz-transform: rotate(3deg); -o-transform: rotate(3deg); -ms-transform: rotate(3deg); transform: rotate(3deg); } </style> </head> <body> <p class="shbox sh-down-lr"> <h2>CSS Demo :before, :after, box-shadow</h2> <p>人最寶貴的是生命。生命屬於人只有一次。人的一生應當這樣度過：當回憶往事的時候，他不會因為虛度年華而悔恨，也不會因為碌碌無為而羞愧.</p> <p>鋼是在烈火裡燃燒、高度冷卻中煉成的，因此它很堅固。我們這一代人也是在鬥爭中和艱苦考驗中鍛鍊出來的，並且學會了在生活中從不灰心喪氣。</p> </p> <p style="background:none;"> <p> <img src="http://photos.tuchong.com/392707/f/6512410.jpg" /> <p> </p> </body> </html>
實現效果：
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