// JavaScript Document
window.onload = newImage;
    MyImages=new Array();
    MyImages[0]='images/thumb_alex.jpg';
    MyImages[1]='images/thumb_ally.jpg';
    MyImages[2]='images/thumb_alfred.jpg';
    MyImages[3]='images/thumb_alla.jpg'; 

    function newImage() 
    {
	if(document.getElementById("mainImage"))
	{
        	document.getElementById("mainImage").setAttribute("src", MyImages[Math.round(Math.random()*3)]);
	}
    
     }