Prova questo. Testato con IE10.
codice HTML:<!DOCTYPE html> <html> <head> </head> <body> <input id='t' type="text"> <script> document.getElementById('t').onkeypress = function(event) { var valore = event.srcElement.value+event.char; if (valore.match(/^[1-9]{1}\d*$|^[1-9]{1}\d*\,\d*$|^0$|^0\,\d*$/) == null) { //event.preventDefault(); return false; } else { return true; } }; </script> </body> </html>