var imagenumber =  7;

var randomnumber = Math.random() ;

var rand = Math.round( (imagenumber-1) * randomnumber) + 1;

banner = new Array

banner[1] = "./randomimages/aspegillus-niger-gfp.jpg"
banner[2] = "./randomimages/fungi2-new.jpg"
banner[3] = "./randomimages/fungi4-new.jpg"
banner[4] = "./randomimages/fungi1-htx.jpg"
banner[5] = "./randomimages/fungi3-htx.jpg"
banner[6] = "./randomimages/fungi5-new.jpg"
banner[7] = "./randomimages/fungi6-new.jpg"

var image = banner[rand]