var mess = new Array
('<img src="img/IMG_5143blue.jpg" alt="Peel P50s, Isle of Man" width="900" height="661">',
'<img src="img/IMG_5143red.jpg" alt="Peel P50s, Isle of Man" width="900" height="661">',
'<img src="img/IMG_5143yellow.jpg" alt="Peel P50s, Isle of Man" width="900" height="661">'
);
var max = mess.length;
var num = Math.floor((Math.random() * max));
document.writeln(mess[num]);