<html xmlns="http://www.w3.org/1999/xhtml" xmlns:xul="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" xmlns:math="http://www.w3.org/1998/Math/MathML"> <head> </head><body><xul:box collapsed="true"><math:mrow><div id="div"> <p id="para">Foo bar</p> </div></math:mrow></xul:box> <script type="application/javascript"> try { document.body.offsetWidth; var para = document.getElementById("para"); var div = document.getElementById("div"); var hbox = document.createElementNS("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul", 'hbox'); div.appendChild(hbox); document.body.offsetWidth; div.removeChild(para); } catch (e) { document.body.appendChild(document.createTextNode(e)); } </script> </body></html>