MyImages=new Array();
    MyImages[0]='Random/1.jpg';
    MyImages[1]='Random/2.jpg';
    MyImages[2]='Random/3.jpg';
	MyImages[3]='Random/4.jpg';
    

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