function editchange(obj) {
  var txt = document.getElementById(obj).value;
  var char;
  var myreturn="";
  var invalidchars = "`";

  for (i=0;i<txt.length;i++) {
	char=txt.charAt(i);
	if (invalidchars.indexOf(char)==-1) myreturn = myreturn+char;
  }
 if (myreturn!=txt) document.getElementById(obj).value = myreturn;
}