// Define images.
if (document.images) {     
   img1on = new Image();      
   img1on.src = "./snape/snape-navmarchivemo.gif"; 
   img1off = new Image();      
   img1off.src = "./snape/snape-navmarchive.gif"; 

   img2on = new Image();      
   img2on.src = "./snape/snape-navaindexmo.gif"; 
   img2off = new Image();      
   img2off.src = "./snape/snape-navaindex.gif"; 

   img3on = new Image();      
   img3on.src = "./snape/snape-navcindexmo.gif"; 
   img3off = new Image();      
   img3off.src = "./snape/snape-navcindex.gif"; 

   img4on = new Image();      
   img4on.src = "./snape/snape-navpindexmo.gif"; 
   img4off = new Image();      
   img4off.src = "./snape/snape-navpindex.gif"; 
}

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

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