if (document.images) {
        img1off=new Image();
        img1off.src="images/introlink1.gif";
        img2off=new Image();
        img2off.src="images/introlink2.gif";
        img3off=new Image();
        img3off.src="images/introlink3.gif";
        img4off=new Image();
        img4off.src="images/introlink4.gif";
        img5off=new Image();
        img5off.src="images/introlink5.gif";

        img1on=new Image();
        img1on.src="images/introlink1a.gif";
        img2on=new Image();
        img2on.src="images/introlink2a.gif";
        img3on=new Image();
        img3on.src="images/introlink3a.gif";
        img4on=new Image();
        img4on.src="images/introlink4a.gif";
        img5on=new Image();
        img5on.src="images/introlink5a.gif";
        }

function imgAct(imgName) {
        if (document.images) {
        document[imgName].src = eval(imgName + "on.src");
        }
}

function imgInact(imgName) {
        if (document.images) {
        document[imgName].src = eval(imgName + "off.src");
        }
}