var mess = new Array('<img src="images/vial_line.jpg" width="160" height="200" border="0">','<img src="images/qtof.jpg" width="160" height="200" border="0">','<img src="images/tof_stack.jpg" width="160" height="200" border="0">');
var max = mess.length;
var num = Math.floor((Math.random() * max));
document.writeln(mess[num]);