if (document.images) {
            var home_off = new Image();
            home_off.src = "imgs/home_off.gif";
            var home_over = new Image();
            home_over.src = "imgs/home_over.gif";
            var company_off = new Image();
            company_off.src = "imgs/company_off.gif";
            var company_over = new Image();
            company_over.src = "imgs/company_over.gif";
			var careers_off = new Image();
            careers_off.src = "imgs/careers_off.gif";
            var careers_over = new Image();
            careers_over.src = "imgs/careers_over.gif";
			var contactus_off = new Image();
            contactus_off.src = "imgs/contactus_off.gif";
            var contactus_over = new Image();
            contactus_over.src = "imgs/contactus_over.gif";
          }

		function switch_on(imgName) {
            if (document.images) {
              document.images[imgName].src = eval(imgName + "_over.src");
              }
          }

          function switch_off(imgName) {
            if (document.images){
              document.images[imgName].src = eval(imgName + "_off.src");
              }
			}