Question

html中调用的js文件错误报告，求高手解答

代码
// JavaScript Document

window.onload = function() {
var oUl = document.getElementById("navt");
var aLi = oUl.getElementsByTagName("li");
var i = 0;
for (i = 0; i < aLi.length; i++) {
aLi[i].timer = null;
aLi[i].speed = 0;
aLi[i].onmouseover = function() {
startMove(this, 250);
};
aLi[i].onmouseout = function() {
startMove2(this, 100);
};
}
};

huo'h错误的报告第五行：TypeError：oUl is null
chrome错误报告也是第五行：Uncaught TypeError: Cannot call method 'getElementsByTagName' of null
求高手解答
function startMove(obj, iTarget) {
if (obj.timer) {
clearInterval(obj.timer);
}
obj.timer = setInterval(function() {
doMove(obj, iTarget);
}, 30)
};

function doMove(obj, iTarget) {
obj.speed += 3;
if (Math.abs(iTarget - obj.offsetWidth) < 1 && Math.abs(obj.speed) < 1) {
clearInterval(obj.timer);
obj.timer = null;
}
else {
if (obj.offsetWidth + obj.speed >= iTarget) {
obj.speed *= -0.7;
obj.style.width = iTarget + "px";
}
else {
obj.style.width = obj.offsetWidth + obj.speed + "px";
}
}
};
问题过长了，发不出来

Answer 1

var oUl = document.getElementById("navt");
var aLi = oUl.getElementsByTagName("li");
这两句话对应的元素有吗

追问

不懂啊，我发下全文件

Answer 2

没有找到元素

追问

我也知道是找不到元素，需要的是如何修改。。。