if (document.images) {

  var btn1na = new Image();
  btn1na.src = "i/btn1na.gif";
  var btn1aa = new Image();
  btn1aa.src = "i/btn1aa.gif";

  var btn2na = new Image();
  btn2na.src = "i/btn2na.gif";
  var btn2aa = new Image();
  btn2aa.src = "i/btn2aa.gif";

  var btn3na = new Image();
  btn3na.src = "i/btn3na.gif";
  var btn3aa = new Image();
  btn3aa.src = "i/btn3aa.gif";

  var btn4na = new Image();
  btn4na.src = "i/btn4na.gif";
  var btn4aa = new Image();
  btn4aa.src = "i/btn4aa.gif";

  var btn5na = new Image();
  btn5na.src = "i/btn5na.gif";
  var btn5aa = new Image();
  btn5aa.src = "i/btn5aa.gif";

  var btn6na = new Image();
  btn6na.src = "i/btn6na.gif";
  var btn6aa = new Image();
  btn6aa.src = "i/btn6aa.gif";

  var btn7na = new Image();
  btn7na.src = "i/btn7na.gif";
  var btn7aa = new Image();
  btn7aa.src = "i/btn7aa.gif";

  var btn8na = new Image();
  btn8na.src = "i/btn8na.gif";
  var btn8aa = new Image();
  btn8aa.src = "i/btn8aa.gif";

  var btn9na = new Image();
  btn9na.src = "i/btn9na.gif";
  var btn9aa = new Image();
  btn9aa.src = "i/btn9aa.gif";
  
  var btn10na = new Image();
  btn10na.src = "i/btn10na.gif";
  var btn10aa = new Image();
  btn10aa.src = "i/btn10aa.gif";  
}

function act(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + "aa.src");
}

function inact(imgName) {
  if (document.images)
    document[imgName].src = eval(imgName + "na.src");
}