<!DOCTYPE html> <style> body { width: 50px; } #test { float: left; display: none; } .block { display: block !important; } </style> <script> window.onload = function () { var test = document.getElementById('test'); test.classList.remove('block'); test.offsetTop; test.classList.add('block'); test.offsetTop; test.classList.remove('block'); test.offsetTop; test.classList.add('block'); test.offsetTop; if (window.testRunner) testRunner.dumpAsText(); }; </script> <body><img src="../resources/50x50.gif"/> <div id="test" class="block">Test passes if no assertion.</div>