img1on = new Image(); img1on.src = 'Images_System/tab_home_on.gif'; 
img1off = new Image(); img1off.src = 'Images_System/tab_home.gif'; 
img2on = new Image(); img2on.src = 'Images_System/tab_myaccount_on.gif'; 
img2off = new Image(); img2off.src = 'Images_System/tab_myaccount.gif'; 
img3on = new Image(); img3on.src = 'Images_System/tab_contactus_on.gif'; 
img3off = new Image(); img3off.src = 'Images_System/tab_contactus.gif'; 
img4on = new Image(); img4on.src = 'Images_System/tab_viewcart_on.gif'; 
img4off = new Image(); img4off.src = 'Images_System/tab_viewcart.gif'; 

saveImg = "";
function showOn(img) {
if (!document.images) return;
if (saveImg != "" && saveImg != img)
showOff(saveImg);
document['img'+img].src = eval('img'+img+'on.src');
saveImg = img;
}
function showOff(img) {
document['img'+img].src = eval('img'+img+'off.src');
}