<html xmlns="http://www.w3.org/1999/xhtml"> <head> <script> function foo() { var newTable = document.createElementNS("http://www.w3.org/1998/Math/MathML", "mtable") document.getElementById("mtr").appendChild(newTable); } </script> </head> <body onload="foo()"> <div> <math xmlns="http://www.w3.org/1998/Math/MathML" display="block"> <mtable> <mtr id="mtr"> <mtd> <mi>x</mi> </mtd> </mtr> </mtable> </math> </div> </body> </html>