// nav 1 image preloads 
image1 = new Image;
image1.src = "images/gradient.png";
image2 = new Image;
image2.src = "images/logo.png";
image3 = new Image;
image3.src = "images/university-hospitals-wolstein-research-building.jpg";
image4 = new Image;
image4.src = "images/casement-house.jpg";
image5 = new Image;
image5.src = "images/harvard-house.jpg";