关于隐藏的浮动导航栏

这是照书上打的代码，不知道哪里有问题，就是没有导航栏出现！！谁能帮帮我啊？谢谢了！<html>
<head>
<title>隐藏的浮动导航面板</title>
<style>
td
{
font-size:14；font-family:'宋体'；color:black;text-align:center
}
a
{
color:black;
}
</style>
</head>
<script language="javascript">
<!--
var menu_width=150;
var show_width=20;
var menu_top=40;
var move_mode='smooth';
//var move_mode='skip';
function addmenuheader()
{
content="<div id='float_menu'";
content+="style='position:absolute;left:0;top:"+menu_top+";";
content+="z_index:50;width:"+eval(menu_width+20+2)+"";
content+="onmouseover='moveOut()' onmouseout='moveBack()'>";
content+="table width='100%' cellpadding='0' cellspacing='1' bgcolor='#555555'>";
content+="<tr height='20'>";
content+="<td bgcolor='#eeffff' width='"+menu_width+"'>";
content+="菜单栏</td>";
content+="<td bgcolor='#c0edcc' rowspan=50 width='"eval(show_width+2)+"'>";
content+="大<br>学<br>链<br>接";
content+="</td></tr>";
document.write(content);
}
function addmenufoot()
{
content="</table></div>";
document.write(content);
}
function additem(text,url,target)
{
    if(!target||target==)
    {
     target="_blank";
     } 
     content="<tr height='20px'><td bgcolor='#eeffff'>";
     content+="<a herf='"+url+"' target='"+target+"'>"+text;
     content+="</a></td></tr>";
     document.write(content);
}
function  moveOut()
{
if(move_mode=='smooth')
{
moveOutSmooth();
}
else
{
moveOutSkip();
}
}
function moveBack()
{
if(move_mode=='smooth')
{
moveOutSmooth();
}
else
{
moveOutSkip();
}
}
function moveOutSmooth()
{
now_pos=parseInt(document.getElementById('float_menu').style.left);
if(window.movingBack)
{
clearTimeout(movingBack);
}
if(now_pos<0)
dx=0-now_pos;
if(dx>30)
document.getElementById('float_menu').style.left=now_pos+5;
else if(dx>10)
document.getElementById('float_menu').style.left=now_pos+2;
else
document.getElementById('float_menu').style.left=now_pos+1;
movingOut=setTimeout("moveOutSmooth()",5);
}
else
{
clearTimeout(window.movingOut);
}
}
function moveOutSkip()
{
if(document.getElementById('float_menu').style.pixelLeft<0)
document.getElementById('float_menu').style.pixelLeft=0;
}
function moveBackSmooth()
{
if(window.movingOut)
{
clearTimeout(movingOut);
}
if(document.getElementById('float_menu').style.pixelLeft>eval(0-menu_width))
dx=document.getElementById('float_menu').style.pixelLeft-eval(0-menu_width);
if(dx>30)
document.getElementById('float_menu').style.pixelLeft-=5;
else if(dx>10)
document.getElementById('float_menu').style.pixelLeft-=2;
else
document.getElementById('float_menu').style.pixelLeft-=1;
movingBack=setTimeout("moveBackSmooth()",5);
}
else
{
clearTimeout(window.movingBack);
}
}
function moveBackSkip()
{
if(document.getElementById('float_menu').style.pixelLeft>eval(0-menu_width))
document.getElementById('float_menu').style.pixelLeft=eval(0-menu_width);
}
function init()
{
addmenuheader();
additem("电科技大","http://www.uestc.edu.cn","_blank");
additem("*******","http://www.uestc.edu.cn","_blank");
additem("*******","http://www.uestc.edu.cn","_blank");
additem("*******","http://www.uestc.edu.cn","_blank");
addmenufoot();
document.getElementById('float_menu').style.left=-menu_width;
document.getElementById('float_menu').style.visibility='visible';
}
//-->
</script>
<body>
网页内容
</body>
<script  language="javascript">
<!--
init();
//-->
</script>
</html>