var active = 'first';    // This is for the currently showing description  
  var hover = false;  // Keep the description only when hovering

  function descShow( show ) {
    if ( !hover && active ) document.getElementById(active).style.display = 'none';
    document.getElementById(show).style.display = 'block';
    active = show;
  }
  
  function descHide( show ) {
    if ( hover ) document.getElementById(show).style.display = 'none';
  }