<html>
<body>
<script type="text/javascript">
function noNumbers(e)
{
var keynum
var keychar
var numcheck

if(window.event) // IE
  {  keynum = e.keyCode
  }
else if(e.which) // Netscape/Firefox/Opera
  {  keynum = e.which
  }
keychar = String.fromCharCode(keynum)
numcheck = /\d/
return !numcheck.test(keychar)
}
</script>

<form>
<input type="text" onkeypress="return noNumbers(event)" />
</form>

</html>