img = new Array;

img[0] = "img/yo_001.gif";
img[1] = "img/yo_002.gif";
img[2] = "img/yo_003.gif";
img[3] = "img/yo_004.gif";
img[4] = "img/yo_005.gif";
img[5] = "img/yo_006.gif";
img[6] = "img/yo_007.gif";
img[7] = "img/yo_008.gif";
img[8] = "img/yo_009.gif";
img[9] = "img/yo_010.gif";
img[10] = "img/yo_011.gif";

function random(){
n = Math.floor(Math.random()*img.length);
document.write("<img src='"+img[n]+"' border='0'>");
}