function toggle_visibility(id) {
       var e = document.getElementById(id);
       if(e.style.visibility == 'visible')
          e.style.visibility = 'hidden';
       else
          e.style.visibility = 'visible';
    }
	
	    function main_visibility(id) {
       var e = document.getElementById(id);
       if(e.style.display == 'none')
          e.style.display = 'block';
       else
          e.style.display = 'none';
    }
	    function main_ofer_visibility(id) {
       var e = document.getElementById(id);
       if(e.style.display == 'block')
          e.style.display = 'none';
       else
          e.style.display = 'block';
    }