Randomly rotating banner

Randomly select an image from an array and display it with an <img> tag. Useful as an advertisement rotator. (Credit: apress.com)

<script type="text/javascript">
var bannerImages = new Array();
bannerImages[0] = "Banner1.jpg";
bannerImages[1] = "Banner2.jpg";
bannerImages[2] = "Banner3.jpg";
bannerImages[3] = "Banner4.jpg";
bannerImages[4] = "Banner5.jpg";
bannerImages[5] = "Banner6.jpg";
bannerImages[6] = "Banner7.jpg";
var randomImageIndex = Math.round(Math.random() * 6);
document.write("<img alt="" src="" + bannerImages[randomImageIndex] + "">");
</script>