if (document.images) {
        img1 = new Image();
        img1.src = "images/link1a.gif";
        img2 = new Image();
        img2.src = "images/link2a.gif";
        img3 = new Image();
        img3.src = "images/link3a.gif";
        img4 = new Image();
        img4.src = "images/link4a.gif";
		img5 = new Image();
        img5.src = "images/link5a.gif";
}

function linkOn(num)
{
document.images['link' + (num)].src = "images/link"+(num)+"a.gif"
}

function linkOff(num)
{
document.images['link' + (num)].src = "images/link"+(num)+".gif"
}


function squareOn(num) {
document.images['square' + (num)].src="images/square_on.gif"
}

function squareOff(num) {
for (i=1; i<16; i++) {
document.images['square' + (i)].src="images/square.gif"
}
document.images['square' + (cnt)].src="images/square_on.gif"
}