Javascript type only number script

<script language=“javascript1.1″>

function isNumberKey(evt)
{
var charCode = (evt.which) ? evt.which : event.keyCode
if (charCode > 31 && (charCode < 48 || charCode > 57)){
alert (“Type Only Number“);
return false;
}

return true;
}

</script>

<input type=“text” onkeypress=“return isNumberKey(event);“ />

<input type=“submit” name=“submit” value=“Save” />