var mess = new Array(
'<img src="images/HeaderImages/header_1.jpg" width="600" height="80" />',
'<img src="images/HeaderImages/header_2.jpg" width="600" height="80" />',
'<img src="images/HeaderImages/header_3.jpg" width="600" height="80" />',
'<img src="images/HeaderImages/header_4.jpg" width="600" height="80" />',
'<img src="images/HeaderImages/header_5.jpg" width="600" height="80" />'
	);
var max = mess.length;
var num = Math.floor((Math.random() * max));
document.writeln(mess[num]);