var imagenumber = 11 ; 
var randomnumber = Math.random() ; 
var rand1 = Math.round( (imagenumber-1) * randomnumber) + 1 ; 
images = new Array 
images[1] = "images/pic_header01.jpg" 
images[2] = "images/pic_header02.jpg" 
images[3] = "images/pic_header03.jpg"
images[4] = "images/pic_header04.jpg"
images[5] = "images/pic_header05.jpg"
images[6] = "images/pic_header06.jpg"
images[7] = "images/pic_header07.jpg"
images[8] = "images/pic_header08.jpg"
images[9] = "images/pic_header09.jpg"
images[10] = "images/pic_header10.jpg"
images[11] = "images/pic_header11.jpg"
var image = images[rand1]