var imagenumber = 4; 

var randomnumber = Math.random() ; 

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

bilder = new Array;

bilder[1] = "fileadmin/template/img/top6.jpg" 

bilder[2] = "fileadmin/template/img/top3.jpg"

bilder[3] = "fileadmin/template/img/top5.jpg"

bilder[4] = "fileadmin/template/img/top7.jpg"

    var bild = bilder[rand1] 

    

    document.write('<img src="' + bild + '" border=0 width=1000 height=195></a>')