MyImages=new Array();
    MyImages[0]='/images/title1.gif';
    MyImages[1]='/images/title2.gif';
    MyImages[2]='/images/title3.gif';
    MyImages[3]='/images/title4.gif';
    MyImages[4]='/images/title5.gif';
    MyImages[5]='/images/title6.gif';
    MyImages[6]='/images/title7.gif';

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