<html> <head> <style> div { display: -moz-box; display: -khtml-box; display: box; background-color: red; width: 100px; height: 100px; } .first { visibility: collapse; -moz-box-flex: 1; -khtml-box-flex: 1; box-flex: 1; width: 50px; height: 100px; } .second { background-color: green; -moz-box-flex: 1; -khtml-box-flex: 1; box-flex: 1; width: 50px; height: 100px; } </style> </head> <body> <p>You should see a 100x100 green square below. If you see any red, the test has failed. This test is checking for visibility:collapse support.</p> <div> <div class="first"></div> <div class="second"></div> </div> </body> </html>