var preloadedImages = new Array();

function preloadImages(locationFolder) {
    if(document.images) {
            var i, args = preloadImages.arguments; 
            for(i=1; i<args.length; i++) {
                preloadedImages[args[i]]   = new Image(); 
                preloadedImages[args[i]].src   = locationFolder + args[i];
            }
    }
}
function rollOn(imageName) {
     if(document.images)
     document.images[imageName].src = preloadedImages[imageName + "_over.gif"].src;
}
function rollOff(imageName) {
    if(document.images)
     document.images[imageName].src = preloadedImages[imageName + "_normal.gif"].src;
}


function rollOnOffDynamic(imageName, newImageName) {
     if(document.images)
        document.images[imageName].src = preloadedImages[newImageName].src;
}