images = new Array(6);
images[0] = "<img src='images/top_01.jpg'>";
images[1] = "<img src='images/top_02.jpg'>";
images[2] = "<img src='images/top_03.jpg'>";
images[3] = "<img src='images/top_04.jpg'>";
images[4] = "<img src='images/top_05.jpg'>";
images[5] = "<img src='images/top_06.jpg'>";
index = Math.floor(Math.random() * images.length);
document.write(images[index]);