<html xmlns="http://www.w3.org/1999/xhtml"> <head> <script> function boom() { document.getElementById("mo").appendChild(document.getElementById("mo2")); document.body.offsetWidth; document.getElementById("span").appendChild(document.createTextNode("baz")); } </script> </head> <body onload="boom();"> <p>Foo <math xmlns="http://www.w3.org/1998/Math/MathML"><mo id="mo2">-</mo></math></p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><msub id="msub"><mo id="mo">+</mo></msub></math> <span id="span">bar</span></p> </body> </html>