function goRand() {
var num = 21;  // количество картинок
myImages = new Array();
myImages[0] = "images/1.jpg";
myImages[1] = "images/2.jpg";
myImages[2] = "images/3.jpg";
myImages[3] = "images/4.jpg";
myImages[4] = "images/5.jpg";
myImages[5] = "images/6.jpg";
myImages[6] = "images/7.jpg";
myImages[7] = "images/8.jpg";
myImages[8] = "images/9.jpg";
myImages[9] = "images/10.jpg";
myImages[10] = "images/11.jpg";
myImages[11] = "images/12.jpg";
myImages[12] = "images/13.jpg";
myImages[13] = "images/16.jpg";
myImages[14] = "images/17.jpg";
myImages[15] = "images/18.jpg";
myImages[16] = "images/19.jpg";
myImages[17] = "images/21.jpg";
myImages[18] = "images/22.jpg";
myImages[19] = "images/23.jpg";
myImages[20] = "images/24.jpg";

rand = Math.floor(Math.random() * num);
current_image = myImages[rand];
document.write("<img src=\"" + current_image + "\" border=\"0\">")
}
goRand();