自己做过的项目从来没有这种东西，但见过别人的项目都有，未免落伍，学来看看，也不知道自己找到的这个是不是正路子，先贴代码再分析。
<!doctype html public "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <style type="text/css" media="all"> a,a:visited {color:#333;text-decoration:none;} a:hover {color:#f60;} body,td {font:13px "Geneva","宋体", "Arial", "Helvetica",sans-serif;} ul,li {margin:0;padding:0;list-style:none;} h1,h2,h3,h4,h5,h6 {margin:0;padding:0;} h1 {padding:5px;color:#900;font:16px bold "Geneva","宋体", "Arial", "Helvetica",sans-serif;} h1 small {font-size:11px;font-weight:normal;color:#660;} .tree_out {width:200px;} .tree_1 .tree_tit a, .tree_1 .tree_tit a:visited, .tree_2 .tree_tit a, .tree_2 .tree_tit a:visited {margin-left:10px;padding-left:40px;color:#003;font-size:12px;display:block;} .tree_2 .tree_tit h3.Lst a {line-height:250%;background: #FF0000;} .tree_2 .tree_txt {display:none;} .tree_1 .tree_txt ul li {padding-left:65px;line-height:150%;} .tree_1 .tree_txt .num {color:#e00;} </style> <script type="text/javascript"> <!-- function ExChgClsName(Obj,NameA,NameB){ var Obj=document.getElementById(Obj)?document.getElementById(Obj):Obj; Obj.className=Obj.className==NameA?NameB:NameA; } function showmenu_tree(iNo){ ExChgClsName("tree_id__"+iNo,"tree_1","tree_2"); } --> </script> </head> <body> <div class="tree_out"> <div class="tree_1" id="tree_id__0"> <div class="tree_tit"><h3><a href="javascript:showmenu_tree(0);">一号主菜单</a></h3></div> <div class="tree_txt"> <ul> <li><a>一号子菜单</a></li> <li><a>二号子菜单</a></li> <li><a>三号子菜单</a></li> <li><a>四号子菜单</a></li> <li class="Lst"><a>五号子菜单</a></li> </ul> </div> </div> <div class="tree_2" id="tree_id__1"> <div class="tree_tit"><h3><a href="javascript:showmenu_tree(1);">二号主菜单</a></h3></div> <div class="tree_txt"> <ul> <li><a>一号子菜单</a></li> <li><a>二号子菜单</a></li> <li><a>三号子菜单</a></li> <li><a>四号子菜单</a></li> <li class="Lst"><a>五号子菜单</a></li> </ul> </div> </div> <div class="tree_2" id="tree_id__2"> <div class="tree_tit"><h3><a href="javascript:showmenu_tree(2);">三号主菜单</a></h3></div> <div class="tree_txt"> <ul> <li><a>一号子菜单</a></li> <li><a>二号子菜单</a></li> <li><a>三号子菜单</a></li> <li><a>四号子菜单</a></li> <li class="Lst"><a>五号子菜单</a></li> </ul> </div> </div> <div class="tree_2" id="tree_id__3"> <div class="tree_tit"><h3><a href="javascript:showmenu_tree(3);">四号主菜单</a></h3></div> <div class="tree_txt"> <ul> <li><a>一号子菜单</a></li> <li><a>二号子菜单</a></li> <li><a>三号子菜单</a></li> <li><a>四号子菜单</a></li> <li class="Lst"><a>五号子菜单</a></li> </ul> </div> </div> </div> </body> </html>
虽说是css + div,但起作用的肯定是javaScript吧，
然后我震惊的发现起作用的就一行代码
Obj.className=Obj.className==NameA?NameB:NameA;
选哪一个就把哪一个div的css换掉。