function preloadImages() {
    h1 = new Image(875, 300);
    h1.src = "/images/header_1.jpg";
    h2 = new Image(875, 300);
    h2.src = "/images/header_2.jpg";
    h3 = new Image(875, 300);
    h3.src = "/images/header_3.jpg";
    h4 = new Image(875, 300);
    h4.src = "/images/header_4.jpg";
    h5 = new Image(875, 300);
    h5.src = "/images/header_5.jpg";
    h6 = new Image(875, 300);
    h6.src = "/images/header_6.jpg";
    h7 = new Image(875, 300);
    h7.src = "/images/header_7.jpg";
}

preloadImages();

function show(intImage) {
    switch (intImage) {
        case 1: document.header.src = h1.src; break;
        case 2: document.header.src = h2.src; break;
        case 3: document.header.src = h3.src; break;
        case 4: document.header.src = h4.src; break;
        case 5: document.header.src = h5.src; break;
        case 6: document.header.src = h6.src; break;
        case 7: document.header.src = h7.src; break;
    }
    return true;
}