懂JS的朋友进来看看！！

不懂JS，不过，需要用到JS，请会的朋友帮我看看下面的代码：
// JScript 文件
var pic_index=1;
var max_index=3;
var inter=null;
inter=setInterval(next,5000);
function changeall() {
for (i=1;i<4;i++) {
eval("tb"+i).style.display="none";
eval("bt"+i).src="Images/news_bt"+i+"1.gif";
}
}
function change(a) {
changeall();
pic_index=a;
eval("tb"+a).style.display="";
eval("bt"+a).src="Images/news_bt"+a+"2.gif";
}
function next(){
pic_index++;
changeall();
if(pic_index>max_index){pic_index=1}
eval("tb"+pic_index).style.display="";
eval("bt"+pic_index).src="Images/news_bt"+pic_index+"2.gif";
}
function prev(){
pic_index--;
changeall();
if(pic_index<1){pic_index=max_index}
eval("tb"+pic_index).style.display="";
eval("bt"+pic_index).src="Images/news_bt"+pic_index+"2.gif";
}
function writeNewsImage(url, img) {
var str = '<a href='+url;
if (-1 < url.indexOf("(") || -1 < url.indexOf("javascript:") )
str+=' target=_self>';
else
str+=' target=_blank>';
str+='<img src='+img+' width=395 height=90 border=0 onmouseout="inter=setInterval(next,2500)"  onmouseover="clearInterval(inter)" /></a>';
document.write(str);
}
function writeNewsTitle(url, des) {
var str = '<a href='+url;
if (-1 < url.indexOf("(") || -1 < url.indexOf("javascript:") )
str+=' target=_self ';
else
str+=' target=_blank ';
str += ' class=news0601 onmouseout="javascript:inter=setInterval(next,2500)" onmouseover="clearInterval(inter)" >';
str += des;
str += '</a>';
document.write(str);
},我的调用该JS文件的代码为：<table border="0" cellpadding="0" cellspacing="0" style="width: 395px; height: 101px">
    <tr>
        <td style="width: 100%; height: 80px">
            <table id="tb1" cellpadding="0" cellspacing="0" style="width:100%;" border="0">
                <tr>
                    <td style="PADDING-RIGHT: 3px; PADDING-LEFT: 7px" vAlign=top>
                    第一块
                    </td>
                </tr>
            </table>
            <table id="tb2" cellpadding="0" cellspacing="0" style="width:100%; display:none;" border="0">
                <tr>
                    <td style="PADDING-RIGHT: 3px; PADDING-LEFT: 7px" vAlign=top>
                    第二块
                    </td>
                </tr>
            </table>
            <table id="tb3" cellpadding="0" cellspacing="0" style="width:100%; display:none;" border="0">
                <tr>
                    <td style="PADDING-RIGHT: 3px; PADDING-LEFT: 7px" vAlign=top>
                    第三块
                    </td>
                </tr>
            </table>
        </td>
    </tr>
    <tr>
        <td style="width: 100%; height: 21px" align="right">
            <table cellSpacing=0 cellPadding=0 style="width:100%;" border=0>
              <tr>
                <td>&nbsp;</td>
                <td width="25"><IMG id=bt1 onmouseover=javascript:clearInterval(inter);change(1) style="CURSOR: hand" onmouseout=javascript:inter=setInterval(next,2500); height=12 src="Images/news_bt12.gif" width=21 border=0 name=bt1></td>
                <td width="25"><IMG onmouseover=javascript:clearInterval(inter);change(2) style="CURSOR: hand" onmouseout=javascript:inter=setInterval(next,2500); height=12 src="Images/news_bt21.gif" width=21 name=bt2></td>
                <td width="25"><IMG onmouseover=javascript:clearInterval(inter);change(3) style="CURSOR: hand" onmouseout=javascript:inter=setInterval(next,2500); height=12 src="Images/news_bt31.gif" width=21 name=bt3></td>
              </tr>
            </table>
        </td>
    </tr>
</table> 
protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.ClientScript.IsClientScriptIncludeRegistered(this.GetType(), "newName"))
        {
            Page.ClientScript.RegisterClientScriptInclude("newName", "Js/PriceScipt.js");
        }
    }
第一次打开页面，显示第一块里面的东西，鼠标放上去后，什么都没有了，不管放哪里，一个块都不显示了！