var imgMax  = 3;
var imgRand = Math.floor(Math.random() * imgMax);
if(imgRand == 0)       document.write('<img src="image/heads_format05.gif"><br>');
else if(imgRand == 1)  document.write('<img src="image/heads_format05.gif"><br>');
else if(imgRand == 2)  document.write('<img src="image/heads_format05.gif"><br>');