var imagenumber = 7 ;
var randomnumber = Math.random() ;
var rand1 = Math.round( (imagenumber-1) * randomnumber) + 1 ;
images = new Array
images[1] = "/images/main_01.jpg"
images[2] = "/images/main_02.jpg"
images[3] = "/images/main_03.jpg"
images[4] = "/images/main_04.jpg"
images[5] = "/images/main_05.jpg"
images[6] = "/images/main_06.jpg"
images[7] = "/images/main_07.jpg"
var image = images[rand1]