function show_hide(bloc,blocimg)
      {
            elt=document.getElementById(bloc);
            if (elt.style.display == 'none') {
                  document.getElementById(bloc).style.display='block';
                  document.getElementById(blocimg).src='../../images/icons/close.gif';
            }
            else {
                  document.getElementById(bloc).style.display='none';
                  document.getElementById(blocimg).src='../../images/icons/open.gif';
            }
      }