if (document.images) {     
    righton = new Image();     
    lefton = new Image();
    righton.src = "images/fastrightsm-light.gif";
    lefton.src = "images/fastleftsm-light.gif";
    rightoff = new Image(); 
    leftoff = new Image();
    rightoff.src = "images/fastrightsmall.gif";
    leftoff.src = "images/fastleftsmall.gif";
}


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

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