// ******************************************************
// Script from Stefan Koch - Voodoo's Intro to JavaScript
//     http://rummelplatz.uni-mannheim.de/~skoch/js/ 
//       JS-book: http://www.dpunkt.de/javascript
//    You can use this code if you leave this message
// ******************************************************

  // ok, we have a JavaScript browser
  var browserOK = false;
  var pics;


  // JavaScript 1.1 browser - oh yes!
  browserOK = true;
  pics = new Array();

var objCount = 0; // number of (changing) images on web-page

function preload(name, first, second) {  

  // preload images and place them in an array

  if (browserOK) {     
    pics[objCount] = new Array(3);
    pics[objCount][0] = new Image();
    pics[objCount][0].src = first;
    pics[objCount][1] = new Image();
    pics[objCount][1].src = second;
    pics[objCount][2] = name;
    objCount++;
  }
}

function on(name){
  if (browserOK) {
     for (i = 0; i < objCount; i++) {
      if (document.images[pics[i][2]] != null)
        if (name != pics[i][2]) { 
          // set back all other pictures
          document.images[pics[i][2]].src = pics[i][0].src;
        } else {
           // show the second image because cursor moves across this image
           document.images[pics[i][2]].src = pics[i][1].src;
        }
    }
  }
}

function off(){
  if (browserOK) {
     for (i = 0; i < objCount; i++) {
      // set back all pictures
      if (document.images[pics[i][2]] != null) 
        document.images[pics[i][2]].src = pics[i][0].src;
    }
  }
}


preload("link1", "images/ct-home1.gif", "images/ct-home2.gif");
preload("link2", "images/ct-toc1.gif", "images/ct-toc2.gif");
preload("link3", "images/ct-quiz1.gif", "images/ct-quiz2.gif");
preload("link4", "images/ct-dis-grp1.gif", "images/ct-dis-grp2.gif");