Various tests for the the hidden IDL attribute. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". The IDL attribute reflects what is present in markup: PASS h1.hidden is true PASS h2.hidden is true PASS h3.hidden is true PASS s1.hidden is false Changes via DOM Core are reflected through the IDL attribute: PASS (h1.removeAttribute("hidden"), h1.hidden) is false PASS (h1.setAttribute("hidden", ""), h1.hidden) is true PASS (h2.setAttribute("hidden", ""), h2.hidden) is true PASS (s1.setAttribute("hidden", ""), s1.hidden) is true Changes via IDL attribute are reflected in the core DOM: PASS (h3.hidden = false, h3.getAttribute("hidden")) is null PASS (h3.hidden = true, h3.getAttribute("hidden")) is "" PASS successfullyParsed is true TEST COMPLETE