if (document.images) {
  var first_off = new Image();
  first_off.src = "../Images/JCMosOff.gif";
  var first_on = new Image();
  first_on.src = "../Images/JCMosOvr.gif";
}
function activate(imgName) {
  if (document.images) {
    if ( eval(imgName + "_on.complete") ) {
      document.images[imgName].src = eval(imgName + "_on.src");
    }
  }
}

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