function hideAll() {
      document.getElementById("imagemap1").visibility = "hidden";
      document.getElementById("imagemap2").visibility = "hidden";
      document.getElementById("imagemap3").visibility = "hidden";
      document.getElementById("imagemap4").visibility = "hidden";


      }
      
function doChange() {
            document.getElementById("imagemap1").style.visibility = "hidden";
            document.getElementById("imagemap2").style.visibility = "hidden";
            document.getElementById("imagemap3").style.visibility = "hidden";
            document.getElementById("imagemap4").style.visibility = "hidden";

			
			
            var selectBox = document.forms[0].changer;

            var user_input = selectBox.options[selectBox.selectedIndex].value;
            document.getElementById(user_input).style.visibility = "visible";
			

	
      }