source: companies/serpro/expressoMail1_2/js/fckeditor/editor/dialog/common/fcknumericfield.htc @ 903

<public:component lightweight="true">

<script language="javascript">

function CheckIsDigit()
{
        var iCode = event.keyCode ;

        event.returnValue =
                (
                        ( iCode >= 48 && iCode <= 57 )          // Numbers
                        || (iCode >= 37 && iCode <= 40)         // Arrows
                        || iCode == 8                                           // Backspace
                        || iCode == 46                                          // Delete
                ) ;

        return event.returnValue ;
}

this.onkeypress = CheckIsDigit ;

</script>

</public:component>