function lightup(imgName)
{
  if (document.images)
  {
    imgOn=eval(imgName + "on.src");
    document[imgName].src= imgOn;
  }
}

function turnoff(imgName)
{
  if (document.images)
  {
    imgOff=eval(imgName + "off.src");
    document[imgName].src= imgOff;
  }
}

if (document.images)
{
  button1on= new Image(180,40);
  button1on.src="images/button1_1.gif"; button1off= new Image(180,40);
  button1off.src="images/button1_0.gif";
  button2on= new Image(180,40);
  button2on.src="images/button2_1.gif"; button2off= new Image(180,40);
  button2off.src="images/button2_0.gif";
  button3on= new Image(180,40);
  button3on.src="images/button3_1.gif"; button3off= new Image(180,40);
  button3off.src="images/button3_0.gif";
  button4on= new Image(180,40);
  button4on.src="images/button4_1.gif"; button4off= new Image(180,40);
  button4off.src="images/button4_0.gif";
  button5on= new Image(180,40);
  button5on.src="images/button5_1.gif"; button5off= new Image(180,40);
  button5off.src="images/button5_0.gif";
  button6on= new Image(180,40);
  button6on.src="images/button6_1.gif"; button6off= new Image(180,40);
  button6off.src="images/button6_0.gif";
}