if (document.images) {
 img1on = new Image(); 
 img1on.src = "images/nav1_f2.gif";   
 img1off = new Image(); 
 img1off.src = "images/nav1.gif"; 
  
 img2on = new Image(); 
 img2on.src = "images/nav2_f2.gif";   
 img2off = new Image(); 
 img2off.src = "images/nav2.gif"; 
  
 img3on = new Image(); 
 img3on.src = "images/nav3_f2.gif";   
 img3off = new Image(); 
 img3off.src = "images/nav3.gif"; 
  
 img4on = new Image(); 
 img4on.src = "images/nav4_f2.gif";   
 img4off = new Image(); 
 img4off.src = "images/nav4.gif"; 
  
 img5on = new Image(); 
 img5on.src = "images/nav5_f2.gif";   
 img5off = new Image(); 
 img5off.src = "images/nav5.gif"; 
    
 }
function imgOn(imgName) {
 if (document.images) {
  document[imgName].src = eval(imgName + "on.src");
 }
}
 
function imgOff(imgName) {
 if (document.images) {
  document[imgName].src = eval(imgName + "off.src");
 }
}