var mess = new Array('<img class="shadow" src="images/p1.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p2.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p3.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p4.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p5.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p6.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p7.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p8.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p9.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p10.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p11.jpg" width="450" height="270" alt="Image" />','<img class="shadow" src="images/p12.jpg" width="450" height="270" alt="Image" />');

var max = mess.length;
var num = Math.floor((Math.random() * max));
document.writeln(mess[num]);               