<!DOCTYPE html>
<style>
body {
margin: 0;
}
.greenbox {
width: 100px;
height: 100px;
background: green;
}
.redbox {
width: 100px;
height: 100px;
background: red;
}
</style>
<body onload="parent.iframeLoadResolve()" contenteditable>
<div class="greenbox"></div>
<div class="redbox"></div>
<div class="greenbox"></div>
<div class="redbox"></div>
<div class="greenbox"></div>
<div class="redbox"></div>
<div class="greenbox"></div>
<div class="redbox"></div>
</body>