<html xmlns="http://www.w3.org/1999/xhtml"><mtr xmlns="http://www.w3.org/1998/Math/MathML"><td id="cell" xmlns="http://www.w3.org/1999/xhtml"></td></mtr><script> function boom() { document.getElementById("cell").contentEditable = true; document.getElementById("cell").focus(); document.execCommand("inserthtml", false, "x"); } window.addEventListener("load", boom, false); </script></html>