// program 4 subnav buttons
		subnav1 = new Image();
		subnav1.src = "images/prog4sub_nav1_lo.jpg";
		subnav1_hi = new Image();
		subnav1_hi.src = "images/prog4sub_nav1_hi.jpg";
		
		subnav2 = new Image();
		subnav2.src = "images/prog4sub_nav2_lo.jpg";
		subnav2_hi = new Image();
		subnav2_hi.src = "images/prog4sub_nav2_hi.jpg";
		
		subnav3 = new Image();
		subnav3.src = "images/prog4sub_nav3_lo.jpg";
		subnav3_hi = new Image();
		subnav3_hi.src = "images/prog4sub_nav3_hi.jpg";
		
		// text
		subnav1_txt = new Image();
		subnav1_txt.src = "images/prog4-1_nav_txt.jpg";
		subnav2_txt = new Image();
		subnav2_txt.src = "images/prog4-2_nav_txt.jpg";
		subnav3_txt = new Image();
		subnav3_txt.src = "images/prog4-3_nav_txt.jpg";