AJAX初级聊天室代码

p;  font-weight: bold;
    line-height: 60px;
    font-family: Tahoma;
    font-size: 12pt;
    float: left;
    width: 100%;
    margin-bottom: 20px;
    filter: Alpha(Opacity=50);
    opacity: 0.5;
}
/*效果*/
.btn{
    border: 1px solid #AAA;
    position: absolute;
    margin-top: 2px;
}
.inputs{
    font-size: 9pt;
    background-image: url(input.png);
    background-repeat: no-repeat;
    width: 295px;
    line-height: 21px;
    height: 21px;
    margin: 0px;
    padding: 0px;
    border: 1px solid #AAA;
}
.left,.right{
    background-repeat: no-repeat;
    background-position: center center;
    cursor:pointer;
    border-top-style: none;
    border-right-style: none;
    border-bottom-style: none;
    border-left-style: none;
    background-color: #FFF;
    height: 23px;
    width: 23px;
}
.left{
    background-image: url(l1.gif);
}
.right{
    background-image: url(r1.gif);
}


JS主文件: 请保存为 images/chat.js
程序代码
var nowNum = "m"
function getId(objId){
    return document.getElementById(objId)
}
function getName(objName){
    return document.getElementsByName(objName)[0]
}
var xmldoc
function createxmldoc(){
    if(window.XMLHttpRequest){
        xmldoc = new XMLHttpRequest();
        if(xmldoc.overrideMimeType){
                xmldoc.overrideMimeType("text/xml");
        }
    }else if(window.ActiveXObject){
        try{
            xmldoc = new ActiveXObject("Msxml4.XMLHTTP");
        }catch(e){
            try{
                xmldoc = new ActiveXObject("Msxml3.XMLHTTP");
            }catch(e){
                try{
                    xmldoc = new ActiveXObject("Msxml2.XMLHT