if (document.images) {
img1on = new Image();
img1on.src = "images/home-on.gif";
img2on = new Image();
img2on.src = "images/announce-on.gif";
img3on = new Image();
img3on.src = "images/assigns-on.gif";
img4on = new Image();
img4on.src = "images/calendar-on.gif";
img5on = new Image();
img5on.src = "images/lectures-on.gif";
img6on = new Image();
img6on.src = "images/resources-on.gif";
img7on = new Image();
img7on.src = "images/refs-on.gif";

img1off = new Image();
img1off.src = "images/home-off.gif";
img2off = new Image();
img2off.src = "images/announce-off.gif";
img3off = new Image();
img3off.src = "images/assigns-off.gif";
img4off = new Image();
img4off.src = "images/calendar-off.gif";
img5off = new Image();
img5off.src = "images/lectures-off.gif";
img6off = new Image();
img6off.src = "images/resources-off.gif";
img7off = new Image();
img7off.src = "images/refs-off.gif";

img1info = new Image(90, 45);
img1info.src = "images/ssdhome.gif";
img2info = new Image(90, 45);
img2info.src = "images/announce.gif";
img3info = new Image(90, 45);
img3info.src = "images/work.gif";
img4info = new Image(90, 45);
img4info.src = "images/calendar.gif";
img5info = new Image(90, 45);
img5info.src = "images/lecture.gif";
img6info = new Image(90, 45);
img6info.src = "images/resources.gif";
img7info = new Image(90, 45);
img7info.src = "images/refs.gif";
    } 

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

function imgOff (imgName) {
	if (document.images) {
		document[imgName].src = eval(imgName + "off.src");
		document["target"].src = "images/spacer.gif";
	}
}