var Ajax = new Object();

Ajax.Request = function(url, id, callbackMethod) {
    if (id == 0) {
        document.getElementById('selSubCat').length = 0;
        document.getElementById('selSubCat').options[0] = new Option("---SUBCATEGORIAS---","0");
        return;
    }
    Page.getPageCenterX();

    Ajax.request = Ajax.createRequestObject();
    Ajax.request.onreadystatechange = callbackMethod;
    Ajax.request.open("POST", url+id, true);
    Ajax.request.send("");
}

Ajax.Response = function () {
    if(Ajax.CheckReadyState(Ajax.request)) {
        document.getElementById('selSubCat').length = 0;
        document.getElementById('selSubCat').options[0] = new Option("---SUBCATEGORIAS---","0");

        var response = Ajax.request.responseXML.documentElement;
        var _data    = response.getElementsByTagName('category');

        if(_data.length == 0) {
            document.getElementById('selSubCat').options[0] = new Option("NO EXISTE SUBCATEGORIA DISPONIBLE", '0');	
        }
        var i
        for ( i = 0 ; i < _data.length ; i ++ ) {
            document.getElementById('selSubCat').options[i+1] = new Option(response.getElementsByTagName('fname')[i].firstChild.data, response.getElementsByTagName('id')[i].firstChild.data);
        }
    }
}

Ajax.createRequestObject = function() {
    var obj;
    if(window.XMLHttpRequest) {
        obj = new XMLHttpRequest();
    }
    else if(window.ActiveXObject) {
        obj = new ActiveXObject("MSXML2.XMLHTTP");
    }
    return obj;
}

Ajax.CheckReadyState = function(obj) {
    if(obj.readyState < 4) {
//        document.getElementById('loading').style.top = (Page.top + Page.height/2)-100;
//        document.getElementById('loading').style.left = Page.width/2-75;
//        document.getElementById('loading').style.position = "absolute";
//        document.getElementById('loading').innerHTML = "<table border=0 cellpadding=0 cellspacing=1 width=160 bgcolor=gray><tr><td align=center class=loading height=45 bgcolor=#ffffff><img src='snake_transparent.gif'/>&nbsp&nbspLoading..</td></tr></table>";  
    }
    //if(obj.readyState == 1) { document.getElementById('loading').innerHTML = "Loading..."; }
    //if(obj.readyState == 2) { document.getElementById('loading').innerHTML = "Loading..."; }
    //if(obj.readyState == 3) { document.getElementById('loading').innerHTML = "Loading..."; }	
    if(obj.readyState == 4) {
        if(obj.status == 200) {
//            document.getElementById('loading').innerHTML = "<table border=0 cellpadding=0 cellspacing=1 width=160 bgcolor=gray><tr><td align=center class=loaded height=45 bgcolor=#ffffff>Data is loaded successfully..</td></tr></table>";
//            setTimeout('Page.loadOut()',1000);
            return true;
        }
        else {
//            document.getElementById('loading').innerHTML = "HTTP " + obj.status;
        }
    }
}

var Page = new Object();
Page.width;
Page.height;
Page.top;

Page.loadOut = function () {
    document.getElementById('loading').innerHTML ='';	
}

Page.getPageCenterX = function () {
        var fWidth;
        var fHeight;
        //For old IE browsers
        if(document.all) {
            fWidth = document.body.clientWidth;
            fHeight = document.body.clientHeight;
        } 
        //For DOM1 browsers
        else if(document.getElementById &&!document.all) {
            fWidth = innerWidth;
            fHeight = innerHeight;
        }
        else if(document.getElementById) {
            fWidth = innerWidth;
            fHeight = innerHeight;
        }
        //For Opera 
        else if (is.op) {
            fWidth = innerWidth;
            fHeight = innerHeight;
        } 
        //For old Netscape 
        else if (document.layers) {
            fWidth = window.innerWidth;
            fHeight = window.innerHeight;
        }
    Page.width = fWidth;
    Page.height = fHeight;
    Page.top = window.document.body.scrollTop;
}