function mastRotator()
{
    // List masthead graphic names
    var mastheadImages = new Array("MountainMast.jpg", "NewMexicoMast.jpg", "PalmSpringsMast.jpg", "VegasMast.jpg");
    // Generate random number to select Masthead
    var randomMast = Math.floor(( Math.random()* mastheadImages.length ));
    // Load masthead in header div
    document.getElementById('header').style.background = "url('graphics/" + mastheadImages[randomMast] + "') no-repeat bottom left";
};