<html style="display: -moz-box; display: -khtml-box; display: box; height:100%; background-color:white">
<body style="margin: 0; display: -moz-box; display: -khtml-box; display: box; -moz-box-flex: 1; -khtml-box-flex: 1; box-flex: 1; background-color:green; color:white">
You should see white text on a green background that fills the window.
</body>
</html>