var JS = {
  start: function(){
	
	$('np_tallas').addEvent('change', function() {
    cat=$('np_tallas').value;
    svcUrl="http://www.naturals-products.com/svc/calcular-peso/" + cat;
      
    var req = new Request.HTML({url:svcUrl, 
    
    onSuccess: function(html) {
        $('cont_pesoideal').set('text', '');
        $('cont_pesoideal').setStyle('display', 'block'); //The w
        $('cont_pesoideal').adopt(html);
      }
    });
  
    req.send();
	});
  

  }
}
window.addEvent('load', JS.start);