richiamare AJAX da pulsante

[metatad]

il resto della pagina (HTML) non è molto rilevante...
questo, invece, è il JavaScript esterno che attiva la funzione:

var indicator_img_path = "indicator.gif";
function init_ibox() {
    var elem_wrapper = "ibox";
    createIbox(document.getElementsByTagName("body")[0]);
    var docRoot = document.getElementsByTagName("a");
    var ibAttr = "rel";     
    var e;
    for (var i = 0; i < docRoot.length - 1; i++) {
            e = docRoot[i];
            if(e.getAttribute(ibAttr)) {
                var t = e.getAttribute(ibAttr);
                if ((t.indexOf("ibox") != -1)  ||  t.toLowerCase() == "ibox") { 
                        e.onclick = function() { 
                            var t = this.getAttribute(ibAttr);
                            var params = parseQuery(t.substr(5,999));
                            var url = this.href;
                            if(this.target != "") {url = this.target} 
                            var title = this.title;
                            showBG();
                            showIbox(url,title,params);
                            return false;
                        }; 
                }
            }
     }
}
var box_w_visible = false;
showBG = function() {
    var box_w = getElem('ibox_w');
    var opacity_level = 8;
    box_w_visible = false;
    box_w.style.opacity = 0;
    box_w.style.filter = 'alpha(opacity=0)';
    for (var i=0;i<=opacity_level;i++) {setTimeout('setOpacity('+i+')',70*i);} 
    setOpacity = function (value)    {
        var box_w = getElem('ibox_w');
        box_w.style.opacity = value/10;
        box_w.style.filter = 'alpha(opacity=' + value*10 + ')';
        if (value == opacity_level) {box_w_visible = true;} 
    }
    box_w.style.display = "";
    var pagesize = new getPageSize();
    var scrollPos = new getScrollPos();
    var ua = navigator.userAgent;
    if(ua.indexOf("MSIE ") != -1) {box_w.style.width = pagesize.width+'px';} 
    else {box_w.style.width = pagesize.width+'px';}
    //box_w.style.height = document.body.scrollHeight+50+'px';
    box_w.style.height = pagesize.height+scrollPos.scrollY+'px';
}
hideBG = function() {
    var box_w = getElem('ibox_w');
    box_w.style.display = "none";bg_opacity = 0;box_w_visible = false;
}
showIndicator = function() {
    var ibox_p = getElem('ibox_progress');
    ibox_p.style.display = "";
    posToCenter(ibox_p);
    ibox_p.onclick = function() {hideIbox();hideIndicator();}
}
hideIndicator = function() {
    var ibox_p = getElem('ibox_progress');
    ibox_p.style.display = "none";
    ibox_p.onclick = null;
}
createIbox = function(elem) {
    var strHTML = "<div id=\"ibox_w\" style=\"display:none;\"></div>";
    strHTML +=    "<div id=\"ibox_progress\" style=\"display:none;\"><img src=\""+indicator_img_path+"\" alt=\"Loading...\"";
    strHTML +=    "style=\"width:128px;height:128px;\"/></div>";
    strHTML +=    "<div id=\"ibox_wrapper\" style=\"display:none\">";
    strHTML +=    "<div id=\"ibox_content\"></div>";
    strHTML +=    "<div id=\"ibox_footer_wrapper\"><div id=\"ibox_close\" style=\"float:right;\">";
    strHTML +=    "<a id=\"ibox_close_a\" href=\"javascript:void(null);\" >[b]<font color=\"#ffffff\">Close Win</font>[/b]</a></div>";
    strHTML +=  "<div id=\"ibox_footer\"></div></div></div></div>";
    var docBody = document.getElementsByTagName("body")[0];
    docBody.style.overflowY = "auto";
    var ibox = document.createElement("div");
    ibox.setAttribute("id","ibox");
    ibox.innerHTML = strHTML;
    elem.appendChild(ibox);
}
var ibox_w_height = 0;
showIbox = function(url,title,params) {
var ibox = getElem('ibox_wrapper');
var ibox_type = 0;

    var ibox_footer = getElem('ibox_footer');
    if(title != "") {ibox_footer.innerHTML = title;} else {ibox_footer.innerHTML = "";}
    var urlString = /\.jpg|\.jpeg|\.png|\.gif|\.html|\.htm|\.php|\.cfm|\.asp|\.aspx|\.jsp|\.jst|\.rb|\.txt/g;
    var urlType = url.match(urlString);
    if(urlType == '.jpg' || urlType == '.jpeg' || urlType == '.png' || urlType == '.gif'){
        ibox_type = 0;
        showIndicator();
        var imgPreloader = new Image();
        imgPreloader.onload = function(){
            var pagesize = new getPageSize();
            var x = pagesize.width - 100;
            var y = pagesize.height - 100;
            if(imgPreloader.width > x) { 
                imgPreloader.height = imgPreloader.height * (x/imgPreloader.width); 
                imgPreloader.width = x; 
                if(imgPreloader.height > y) { 
                    imgPreloader.width = imgPreloader.width * (y/imgPreloader.height); 
                    imgPreloader.height = y; 
                }
            } 
            else if(imgPreloader.height > y) { 
                imgPreloader.width = imgPreloader.width * (y/imgPreloader.height); 
                imgPreloader.height = y; 
                if(imgPreloader.width > x) { 
                    imgPreloader.height = imgPreloader.height * (x/imgPreloader.width); 
                    imgPreloader.width = x;
                }
            }
            hideIndicator();    
            var strHTML = "<a href=\"javascript:void(null);\"><img src=\""+url+"\" style=\"width:"+imgPreloader.width+"px;height:"+imgPreloader.height+"px;border:0;\"/></a>";
            setIBoxContent(strHTML);    
            ibox.style.height = imgPreloader.height+'px';
            ibox.style.width = imgPreloader.width+'px';
            ibox.style.display = "";
            ibox.style.visibility = "hidden";
            posToCenter(ibox); 
            ibox.style.visibility = "visible";
        }
        imgPreloader.src = url;
    } else if(url.indexOf("#") > 0) {
            var strHTML = "";
            ibox_type = 1;
            var elemSrcId = url.substr(url.indexOf("#") + 1,1000);
            var elemSrc = getElem(elemSrcId);
            if(elemSrc) {
                strHTML = elemSrc.innerHTML;
            }
            setIBoxContent(strHTML);
            if(params['height']) {ibox.style.height = params['height']+'px';} 
            else {ibox.style.height = '280px';}
            if(params['width']) {ibox.style.width = params['width']+'px';} 
            else {ibox.style.width = '450px';}
            ibox.style.display = "";
            ibox.style.visibility = "hidden";
            posToCenter(ibox); 
            ibox.style.visibility = "visible";
    }else if(urlType=='.htm'||urlType=='.html'||urlType=='.php'||
             urlType=='.asp'||urlType=='.aspx'||urlType=='.jsp'||
             urlType=='.jst'||urlType=='.rb'||urlType=='.txt'||
             urlType=='.cfm') {
            ibox_type = 2;
            showIndicator();
            http.open('get',url,true);
            http.onreadystatechange = function() {
                if(http.readyState == 4){
                    var response = http.responseText;
                    setIBoxContent(response);
                    hideIndicator();
                    if(params['height']) {ibox.style.height = params['height']+'px';} 
                    else {ibox.style.height = '280px';}
                    if(params['width']) {ibox.style.width = params['width']+'px';} 
                    else {ibox.style.width = '450px';}
                    ibox.style.display = "";
                    ibox.style.visibility = "hidden";
                    posToCenter(ibox); 
                    ibox.style.visibility = "visible";
                }
            }
            http.setRequestHeader("Content-Type","application/x-www-form-urlencoded; charset=UTF-8");
            http.send(null);
    } 
    ibox.style.opacity = 0;
    ibox.style.filter = 'alpha(opacity=0)';    
    var ibox_op_level = 10;
    for (var i=0;i<=ibox_op_level;i++) {setTimeout('setIboxOpacity('+i+')',30*i);}
    setIboxOpacity = function (value)    {
        var ibox = getElem('ibox_wrapper');
        ibox.style.opacity = value/10;
        ibox.style.filter = 'alpha(opacity=' + value*10 + ')';
    }
    if(ibox_type == 1 || ibox_type == 2) {
        ibox.onclick = null;
        getElem("ibox_close_a").onclick = function() {hideIbox();}
    } else {
        ibox.onclick = hideIbox;
        getElem("ibox_close_a").onclick = null;
    }
    window.onscroll = maintPos;
}
maintPos = function() {
    var ibox = getElem('ibox_wrapper');
    var box_w = getElem('ibox_w');
    var pagesize = new getPageSize();
    var ua = navigator.userAgent;
    if(ua.indexOf("MSIE ") != -1) {box_w.style.width = pagesize.width+'px';} 
    else {box_w.style.width = pagesize.width+'px';}
    box_w.style.height = document.body.scrollHeight+'px';
    posToCenter(ibox);
}
hideIbox = function() {
    hideBG();
    var ibox = getElem('ibox_wrapper');
    ibox.style.display = "none";
    clearIboxContent();
    window.onscroll = null;
}
posToCenter = function(elem) {
    var scrollPos = new getScrollPos();
    var pageSize = new getPageSize();
    var emSize = new getElementSize(elem);
    var x = Math.round(pageSize.width/2) - (emSize.width /2) + scrollPos.scrollX;
    var y = Math.round(pageSize.height/2) - (emSize.height /2) + scrollPos.scrollY;    
    elem.style.left = x+'px';elem.style.top = y+'px';
}
getScrollPos = function() {
    var docElem = document.documentElement;
    this.scrollX = self.pageXOffset || (docElem&&docElem.scrollLeft) || document.body.scrollLeft;
    this.scrollY = self.pageYOffset || (docElem&&docElem.scrollTop) || document.body.scrollTop;
}
getPageSize = function() {
        var docElem = document.documentElement
        this.width = self.innerWidth || (docElem&&docElem.clientWidth) || document.body.clientWidth;
        this.height = self.innerHeight || (docElem&&docElem.clientHeight) || document.body.clientHeight;
}
getElementSize = function(elem) {
    this.width = elem.offsetWidth ||  elem.style.pixelWidth;
    this.height = elem.offsetHeight || elem.style.pixelHeight;
}
setIBoxContent = function(str) {
    clearIboxContent();
    getElem('ibox_content').innerHTML = str;
}
clearIboxContent = function() {
    getElem('ibox_content').innerHTML = "";
}
getElem = function(elemId) {
    return document.getElementById(elemId);    
}
parseQuery = function(query) {
   var Params = new Object ();
   if (!query) return Params; 
   var Pairs = query.split(/[;&]/);
   for ( var i = 0; i < Pairs.length; i++ ) {
      var KeyVal = Pairs[i].split('=');
      if ( ! KeyVal || KeyVal.length != 2 ) continue;
      var key = unescape( KeyVal[0] );
      var val = unescape( KeyVal[1] );
      val = val.replace(/\+/g, ' ');
      Params[key] = val;
   }
   return Params;
}
createRequestObject = function() {
    var xmlhttp;
    if (!xmlhttp && typeof XMLHttpRequest != "undefined") {
            try {xmlhttp = new XMLHttpRequest();} catch (e) {xmlhttp = false;}
    }
    return xmlhttp;
}
var http = createRequestObject();
function addEvent(obj, evType, fn){ 
 if (obj.addEventListener){ 
   obj.addEventListener(evType, fn, false); 
   return true; 
 } else if (obj.attachEvent){ 
   var r = obj.attachEvent("on"+evType, fn); 
   return r; 
 } else { 
   return false; 
 } 
}
addEvent(window, 'load', init_ibox); 

Spero serva a capire.