images = new Array(10);

images[0] = "<img src='images/random/0.jpg' alt='banner image'>";
images[1] = "<img src='images/random/1.jpg' alt='banner image'>";
images[2] = "<img src='images/random/2.jpg' alt='banner image'>";
images[3] = "<img src='images/random/3.jpg' alt='banner image'>";
images[4] = "<img src='images/random/4.jpg' alt='banner image'>";
images[5] = "<img src='images/random/5.jpg' alt='banner image'>";
images[6] = "<img src='images/random/6.jpg' alt='banner image'>";
images[7] = "<img src='images/random/7.jpg' alt='banner image'>";
images[8] = "<img src='images/random/8.jpg' alt='banner image'>";
images[9] = "<img src='images/random/9.jpg' alt='banner image'>";

index = Math.floor(Math.random() * images.length);

document.write(images[index]);