网页设计中常用的二级导航菜单特效，符合web标准：
<!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> <title>Horizontal Drop Down Menus</title> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <script type=text/javascript> /** *菜单的构造,需要绑定到onload */ startList = function() { if (document.all&&document.getElementById) { dropmenuRoot = document.getElementById("dropmenu"); for (i=0; i<dropmenuRoot.childNodes.length; i++) { node = dropmenuRoot.childNodes[i]; if (node.nodeName=="LI") { node.onmouseover=function() { this.className+=" over"; //开始灌水 for(j=0;j<this.childNodes.length;j++){ if (this.childNodes[j].nodeName=="UL"){ if (this.childNodes[j].childNodes[0].nodeName=="LI"){ if (this.offsetLeft+this.childNodes[j].childNodes.length*this.childNodes[j].childNodes[0].offsetWidth-dropmenuRoot.offsetLeft>dropmenuRoot.offsetWidth){ var len=this.childNodes[j].childNodes.length*this.childNodes[j].childNodes[0].offsetWidth; //菜单的长度 (len>dropmenuRoot.offsetWidth) ? this.childNodes[j].style.width=776+"px" : this.childNodes[j].style.width=len+"px"; //给ul设置宽度 如果子菜单比较多，大于容器的宽度，那么ul的宽度就是容器的宽度 len =this.offsetLeft+len-dropmenuRoot.offsetLeft-dropmenuRoot.offsetWidth; (len>this.offsetLeft-dropmenuRoot.offsetLeft) ? this.childNodes[j].style.marginLeft=-(this.offsetLeft-dropmenuRoot.offsetLeft) : this.childNodes[j].style.marginLeft=-len+"px"; } } } } } //灌水完毕 node.onmouseout=function() { this.className=this.className.replace(" over", ""); } } } } } window.onload=startList; </script> </head> <style type="text/css"> body { font: normal 11px verdana; background: #45b97c; position:absolute } ul { margin: 0; padding: 0; } li { list-style-position: outside; list-style: none;} a { text-decoration: none; color: #666;} ul#dropmenu,ul#dropmenu ul{ margin: 0 auto; text-align: left; padding: 0; list-style: none; z-index: 99; } ul#dropmenu { width: 774px; display: block; height: 24px; clear: both; border: 1px solid #ccc; text-align: center; background: #fff; } ul#dropmenu li { position: relative; z-index: 999; float: left; } ul#dropmenu ul li{ float: left; display: block; } ul#dropmenu ul { /*width: 122px; w\idth: 120px;*/ height: auto; position: absolute; text-align: left; left: 0px; display: none; border: solid 1px #ccc; } /*当鼠标在子菜单和父菜单上时，父菜单的样式*/ ul#dropmenu li.over a,ul#dropmenu li:hover a{ border-color: #ccc; background: #c00; color: #fff; } /*将子菜单的样式清除*/ ul#dropmenu li.over ul a,ul#dropmenu li:hover ul a{ font-weight: normal; color: #666; background: #fff;; } /*子菜单的hover样式*/ ul#dropmenu li.over ul a:hover,ul#dropmenu li:hover ul a:hover{ font-weight: normal; color: #cc0000; font-weight: bold; background: #f6f6f6; } /* Styles for Menu Items */ ul#dropmenu a { display: block; padding: 0 0 0 10px; width: 106px; w\idth: 96px; color: #666; line-height: 24px; } ul#dropmenu ul li{ width: 110px; border: 0; } /* End */ ul#dropmenu ul a { FILTER: progid:DXImageTransform.Microsoft.Alpha(opacity=70); /* 透明 */ padding: 2px 0px 2px 10px; border: 0; width: 120px; w\idth: 110px;/* Sub Menu Styles */ } ul#dropmenu li:hover ul,ul#dropmenu li.over ul { display: block; /* The magic */ } </style> <body> <div id="nav"> <ul id="dropmenu"> <li><a href="#">Home</a></li> <li><a href="#">About</a> <ul> <li><a href="#">History</a></li> <li><a href="#">Team</a></li> <li><a href="#">Drop Down Menu</a></li> <li><a href="#">Offices</a></li> </ul> </li> <li><a href="#">Services</a> <ul> <li><a href="#">History</a></li> <li><a href="#">Team</a></li> <li><a href="#">Drop Down Menu</a></li> <li><a href="#">Offices</a></li> </ul> </li> <li><a href="#">Home</a></li> <li><a href="#">About</a> <ul> <li><a href="#">History</a></li> <li><a href="#">Team</a></li> <li><a href="#">Drop Down Menu</a></li> <li><a href="#">Offices</a></li> <li><a href="#">History</a></li> <li><a href="#">Team</a></li> </ul> </li> <li><a href="#">Services</a> <ul> <li><a href="#">History</a></li> <li><a href="#">Team</a></li> <li><a href="#">Drop Down Menu</a></li> <li><a href="#">Offices</a></li> <li><a href="#">History</a></li> <li><a href="#">Team</a></li> <li><a href="#">Drop Down Menu</a></li> <li><a href="#">Offices</a></li> <li><a href="#">History</a></li> <li><a href="#">Team</a></li> <li><a href="#">Drop Down Menu</a></li> </ul> </li> <li><a href="#">Home</a></li> </ul> </div> </body> </html>
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