使用javascript更改可见性

hi我有一个使用ajax从另一个页面检索数据的网页，在这样做的同时，我想在页面中显示一个加载gif，所以我创建了一个带有gif的div。

 <div id="loading"><img src="images/loadinfo.net.gif" width="48" height="48" /></div>

这是我的css代码：

#content #loading {
    visibility:hidden;
    position: fixed;
    width: 48px;
    top: 0px;
}

现在，我想我所需要做的就是在加载内容ajax函数开始时将加载div的可见性设置为"visible"，然后在最后将其再次隐藏但奇怪的是，如果我创建可见的加载div，然后在ajax函数开始时将其隐藏，它就可以正常工作了！！！

这是我的功能：

function ajaxpage(url, containerid) {
    document.getElementById('loading').style.visibility = 'visible';
    var bustcachevar = 1 //bust potential caching of external pages after initial request? (1=yes, 0=no)
    var loadedobjects = ""
    var rootdomain = "http://" + window.location.hostname
    var bustcacheparameter = ""
    var page_request = false
    if (window.XMLHttpRequest) // if Mozilla, Safari etc
    page_request = new XMLHttpRequest()
    else if (window.ActiveXObject) { // if IE
        try {
            page_request = new ActiveXObject("Msxml2.XMLHTTP")
        } catch (e) {
            try {
                page_request = new ActiveXObject("Microsoft.XMLHTTP")
            } catch (e) {}
        }
    } else
    return false
    page_request.onreadystatechange = function () {
        loadpage(page_request, containerid)
    }
    if (bustcachevar) //if bust caching of external page
    bustcacheparameter = (url.indexOf("?") != -1) ? "&" + new Date().getTime() : "?" + new Date().getTime()
    page_request.open('GET', url + bustcacheparameter, true)
    page_request.send(null)
}
function loadpage(page_request, containerid) {
    if (page_request.readyState == 4 && (page_request.status == 200 || window.location.href.indexOf("http") == -1)) document.getElementById(containerid).innerHTML = page_request.responseText
}
function loadobjs() {
    if (!document.getElementById) return
    for (i = 0; i < arguments.length; i++) {
        var file = arguments[i]
        var fileref = ""
        if (loadedobjects.indexOf(file) == -1) { //Check to see if this object has not already been added to page before proceeding
            if (file.indexOf(".js") != -1) { //If object is a js file
                fileref = document.createElement('script')
                fileref.setAttribute("type", "text/javascript");
                fileref.setAttribute("src", file);
            } else if (file.indexOf(".css") != -1) { //If object is a css file
                fileref = document.createElement("link")
                fileref.setAttribute("rel", "stylesheet");
                fileref.setAttribute("type", "text/css");
                fileref.setAttribute("href", file);
            }
        }
        if (fileref != "") {
            document.getElementsByTagName("head").item(0).appendChild(fileref)
            loadedobjects += file + " " //Remember this object as being already added to page
        }
    }
    document.getElementById('loading').style.visibility = 'hidden';
}