function image() { };  
   image = new image(); 
   number = 0;
   // imageArray 
   image[number++] = "<img src='../img/main-graphic.jpg' border='0'>" 
   image[number++] = "<img src='../img/main-graphic3.jpg' border='0'>" 
   image[number++] = "<img src='../img/main-graphic4.jpg' border='0'>" 

increment = Math.floor(Math.random() * number);  document.write(image[increment]);