给以某网站域名链接开头的a标签、超链接添加图标logo

#main #content a[href^="http://yuncode.net"]{
    letter-spacing:0;
    font-size: 14px;
    padding:3px 0 3px 27px;
    background:url(images/url_yuncode_icon.png) no-repeat -155px -329px;
}