ajax - XMLHttpRequest access denied

Question

I got problem with request in ajax. I wrote site script like that:

var url = "http://url/api/render";
if (window.XMLHttpRequest) { //
        http = new XMLHttpRequest();
        if (http.overrideMimeType) {
            http.overrideMimeType('text/xml');
        }
    } else if (window.ActiveXObject) {//ie
        try {
            http = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
            try {
                http = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (e) {}
        }
    }
http.open('POST', url, false);

After call the function, I got "Access denied" error. What I do wrong ? For testing I typed google address ... this same error