var mess = new Array('<img class="img-header" src="banner/cabbage_field.jpg" alt=""/>','<img class="img-header" src="banner/extension.jpg" alt=""/>','<img class="img-header" src="banner/home_ec.jpg" alt=""/>','<img class="img-header" src="banner/water_management.jpg" alt=""/>');
var max = mess.length;
var num = Math.floor((Math.random() * max));
document.writeln(mess[num]);