js有几个缺陷。combox1.doSelectIdx(-1)我看不用调用了。

function getLeftPostion( theObj )
{
    var pos = 0;
    while ( theObj != null )
    {
    pos += theObj.offsetLeft;
    //get the Object which contain theObj.
    theObj = theObj.offsetParent;
    }
    return pos;
}
function getTopPostion( theObj )
{
    var pos = 0;
    while ( theObj != null )
    {
    pos += theObj.offsetTop;
    //get the Object which contain theObj.
    theObj = theObj.offsetParent;
    }
    return pos;
}
function checkVersion()
{
    var isBadVersion=true;
    var curVer=navigator.appVersion;
    var pos=parseInt(curVer.indexOf("MSIE"));
    if (pos>=1)
    {
    var intVer=parseInt(curVer.charAt(pos+5));
    if (intVer>=5)
    { isBadVersion=false;}
    }
    if (isBadVersion)
    {
    var msg="This page may not be displayed properly:
"+
       " This product requires Microsoft Internet Explorer 5 or later browser only.";
    alert(msg);
    }
}
//check the browser version
checkVersion();
// the array of comboBoies
theArray = new Array();
function combobox(objId, objHandler)
{
    this.comObj = document.all[objId];
    //this.comObj.selectedIndex = -1;    我觉得可以去掉这一句