<html> <head> <style> div.box { height: 100px; background-color:green; display: -moz-box; display: -khtml-box; display: box; } </style> </head> <body> You should see a green rectangle below that is 100 pixels tall and that fills the width of the content area. If you see any red, then the test has failed. <div style="background-color:red;height:100px"> <div class="box"></div></div></div> </body> </html>