if (document.images) { 
img1on = new Image();
img1on.src = "./images/an_logo.gif"; 
img1off = new Image(); 
img1off.src = "./images/main_20.jpg"; 
img2on = new Image();
img2on.src = "./images/an_logo.gif"; 
img2off = new Image(); 
img2off.src = "./images/main_22.jpg";
}
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");}
}