var img1 = "pics/password1.gif"
var img2 = "pics/password2.gif"
var img3 = "pics/password3.gif"
var img4 = "pics/password4.gif"

var randomize = Math.round(Math.random()*6) 

if (randomize == 1){ 
newimg = img1 
}else if (randomize == 2){ 
newimg = img2 
}else if (randomize == 3){ 
newimg = img3
}else{ newimg = img4 
}
document.write('<IMG SRC="'+newimg+'">') // JavaScript Document