<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"> <html> <head> <style> .green { width: 100px; height: 100px; background-color: green; } .red { width: 100px; height: 100px; background-color: red; margin-top:100px; } .overflow { overflow: hidden; } </style> <body> You should see a 100x100 green square below. If you see any red, the test has failed. <div class="green overflow"><div class="red"></div></div>