img = new Array(1); 
img[0] = "<center><a href=http://www.transtelford.pl><img src='http://www.rkubica.net/obrazy/380c93b18b3acc59f9ca7468dade2035.jpg'  style='vertical-align: middle; padding-top:10px;'></a></center>";
index = Math.floor(Math.random() * img.length);
document.write( img[index] );