document.domain = "example.org"; function $(str) { return document.getElementById(str); } function hookLoad(str) { $(str).onload = function() { window.parent.parent.postMessage("end", "*"); }; window.parent.parent.postMessage("start", "*"); } window.onload = function() { hookLoad("w"); $("w").contentWindow.location.href = "test1.example.org.png"; hookLoad("x"); var doc = $("x").contentDocument; doc.write(''); doc.close(); }; function doIt() { hookLoad("y"); $("y").contentWindow.location.href = "example.org.png"; hookLoad("z"); var doc = $("z").contentDocument; doc.write(''); doc.close(); } window.addEventListener("message", doIt);