var imagenumber = 21 ;
var randomnumber = Math.random() ;
var rand1 = Math.round( (imagenumber-1) * randomnumber) + 1 ;

images = new Array
images[1] = '/img/postere/random/01.jpg'
images[2] = '/img/postere/random/02.jpg'
images[3] = '/img/postere/random/03.jpg'
images[4] = '/img/postere/random/04.jpg'
images[5] = '/img/postere/random/05.jpg'
images[6] = '/img/postere/random/06.jpg'
images[7] = '/img/postere/random/07.jpg'
images[8] = '/img/postere/random/08.jpg'
images[9] = '/img/postere/random/09.jpg'
images[10] = '/img/postere/random/10.jpg'
images[11] = '/img/postere/random/11.jpg'
images[12] = '/img/postere/random/12.jpg'
images[13] = '/img/postere/random/13.jpg'
images[14] = '/img/postere/random/14.jpg'
images[15] = '/img/postere/random/15.jpg'
images[16] = '/img/postere/random/16.jpg'
images[17] = '/img/postere/random/17.jpg'
images[18] = '/img/postere/random/18.jpg'
images[19] = '/img/postere/random/19.jpg'

var image = images[rand1]
document.write("<img src='" +image+ "' alt='WildClimb Poster' style='margin-top:10px;'>")