function change_practic(rewrite) {
   var div_practic = document.getElementById('practic-'+rewrite);
   if (div_practic && div_practic.style.display=='none') {
      var divs = div_practic.parentNode.getElementsByTagName('div');
      for (var i=0 ; i<divs.length ; i++) {
         if (divs[i].className=='practic_description') {
            divs[i].style.display='none';
         }
      }
      Effect.toggle('practic-'+rewrite, 'appear');
   }
}