Test that iframe.contentWindow.document.write() can convert a document to strict mode -- https://bugs.webkit.org/show_bug.cgi?id=24336 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". about:blank is quirksmode by default PASS iframeDocument.compatMode is "BackCompat" ensure that about:blank's DOM has an html and body element PASS treeAsString(iframeDocument) is "#document [HTML [HEAD, BODY]]" writing a doctype as the first document.write can change the document to standards PASS iframeDocument.compatMode is "CSS1Compat" ensure the written DOM has an html and body element PASS treeAsString(iframeDocument) is "#document [html, HTML [HEAD, BODY [#text]]]" ensure that document.open clears the document but does not change the document pointer PASS iframeDocument is iframe.contentWindow.document document.open should also clear the document and reset the doctype) PASS treeAsString(iframeDocument) is "#document" PASS iframeDocument.compatMode is "CSS1Compat" document.write of "" should leave the document in no-quirks mode and add no content to the document PASS iframeDocument.compatMode is "CSS1Compat" PASS treeAsString(iframeDocument) is "#document" document.write calls can change the doctype until an is created PASS iframeDocument.compatMode is "CSS1Compat" reset the document again document.write of "" should leave the document in quirksmode and add only an HTML element, no body PASS iframeDocument.compatMode is "BackCompat" PASS treeAsString(iframeDocument) is "#document [HTML]" any document.write calls after has been encountered cannot change the doctype PASS iframeDocument.compatMode is "BackCompat" PASS successfullyParsed is true TEST COMPLETE