showDiv = function(num) { 
  toFind = 'nr'+num; 
  for (i=0; i<document.getElementsByTagName("div").length; i++) { 
    ourNode = document.getElementsByTagName("div")[i];
    if (ourNode.id == toFind) {
      ourNode.style.display = 'block'; 
    } else { 
      if (ourNode.id.substr(0,2) == toFind.substr(0,2)) { 
        ourNode.style.display = 'none'; 
      }
    }
  }
}
hideDiv = function(num) { 
  toFind = 'nr'+num; 
  for (i=0; i<document.getElementsByTagName("div").length; i++) { 
    ourNode = document.getElementsByTagName("div")[i];
    if (ourNode.id == toFind) {
      ourNode.style.display = 'none'; 
    }
  }
}