window.onload =function(){

var x = document.getElementById("ul1");

var y = x.getElementsByTagName("li");

var z = document.getElementById("tab-list").getElementsByTagName("div");

for(var i=0;i<y.length;i++){

????y[i].index = i;

????y[i].onmouseover = function(){

????for(var i = 0; i < y.length; i++) { y[i].className = ""; }

? ? ? ? ? ? ? ? this.className = "active";

????for(var j = 0; j < z.length; j++) {z[j].className = "hide"; }

? ? ? ? ? ? ? ? z[this.index].className = "show";

????????}

????}

}

y和z的長度都是3，這里把

?for(var i = 0; i < y.length; i++) { y[i].className = ""; }

????????和

for(var j = 0; j < z.length; j++) {z[j].className = "hide"; }

循環合并，怎么就不行了？