if (document.images) {
		
		// on images
		img1on = new Image();
		img1on.src = "images/ellen_buttons_AutoCAD_on.gif";
		img2on = new Image();
		img2on.src = "images/ellen_buttons_PowerPoint_on.gif";
		img4on = new Image();
		img4on.src = "images/ellen_buttons_About_on.gif";
		img5on = new Image();
		img5on.src = "images/ellen_buttons_Links_on.gif";
		img6on = new Image();
		img6on.src = "images/tips_buttons_pp_on.gif";
		img7on = new Image();
		img7on.src = "images/tips_buttons_r2_c1_f2.gif";
		img8on = new Image();
		img8on.src = "images/tips_buttons_r3_c1_f2.gif";

		img10on = new Image();
		img10on.src = "images/bookstore_on.gif";

		img11on = new Image();
		img11on.src = "images/portfolio_button_on.gif";
		img12on = new Image();
		img12on.src = "images/tips_buttons_powerpoint_tips_blog_on.gif";
		
		// off images
		img1off = new Image();
		img1off.src = "images/ellen_buttons_AutoCAD_off.gif";
		img2off = new Image();
		img2off.src = "images/ellen_buttons_PowerPoint_on.gif";
		img4off = new Image();
		img4off.src = "images/ellen_buttons_About_off.gif";
		img5off = new Image();
		img5off.src = "images/ellen_buttons_Links_off.gif";
		img6off = new Image();
		img6off.src = "images/tips_buttons_pp_off.gif";
		img7off = new Image();
		img7off.src = "images/tips_buttons_r2_c1.gif";
		img8off = new Image();
		img8off.src = "images/tips_buttons_r3_c1.gif";
	
		img10off = new Image();
		img10off.src = "images/bookstore_off.gif";

		img11off = new Image();
		img11off.src = "images/portfolio_button_off.gif";
		img12off = new Image();
		img12off.src = "images/tips_buttons_powerpoint_tips_blog_off.gif";

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