images = new Array(3);

images[0] = "<a href='http://goterriers.cstv.com'><img src='http://grfx.cstv.com/schools/bost/graphics/bost-07-mast-index-1.gif' alt='bost' border='0' class='noborder'></a>";

images[1] = "<a href='http://goterriers.cstv.com'><img src='http://grfx.cstv.com/schools/bost/graphics/bost-07-mast-index-2.gif' alt='bost' border='0' class='noborder'></a>";

images[2] = "<a href='http://goterriers.cstv.com'><img src='http://grfx.cstv.com/schools/bost/graphics/bost-07-mast-index-3.gif' alt='bost' border='0' class='noborder'></a>";

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

document.write(images[index]);