<script type="text/javascript">
function onlyNumber(evt) {
     var theEvent = evt || window.event;
     var key = theEvent.keyCode || theEvent.which;
     key = String.fromCharCode( key );
     var regex = /[0-9]|\./;
   if( !regex.test(key) ) {
    theEvent.returnValue = false;
    alert(key + "   Это не число");
    if(theEvent.preventDefault) theEvent.preventDefault();
  }
};

function KeyPress(e,element)
   {
      var kk = navigator.appName == ''Netscape'' ? e.which : e.keyCode;
      if (kk == 13)
      {
         document.submain.elements[element].focus();
         return false
      }
      return true
   };
 </script>

onKeyPress="onlyNumber(event); return KeyPress(event, 1);"

if (kk == 13 || kk == 39)

var regex = /[0-9]|\./;