var bannerImages = ['banner_about_1.jpg', 'banner_about_3.jpg', 'banner_it_prof.jpg'];
var currentCount = 0;

function nextImage() {
    currentCount++;
    if (currentCount >= bannerImages.length) {
        currentCount = 0;
    }
    var banner = document.getElementById("banner");
    if (banner) {
        banner.src = 'images/banner/' + bannerImages[currentCount];
    }
}

function periodicChangeImage() {
    window.setInterval("nextImage()", 3000);
}

if (window.addEventListener) {
    window.addEventListener("load", periodicChangeImage, false);
} else if (window.attachEvent) {
    window.attachEvent('onload', periodicChangeImage);
}