Il titolo c'azzeca nulla col contenuto

codice:
<script type="text/javascript">

image = new Array();
number = 0;
// imageArray

image[number++] = "[img]/img/1.png[/img]"
image[number++] = "[img]/img/2.png[/img]"
image[number++] = "[img]/img/3.png[/img]"
image[number++] = "[img]/img/4.png[/img]"

imgrdn1 = Math.floor(Math.random() * number);
imgrdn2 = (imgrdn1+1)%number;
imgrdn3 = (imgrdn2+1)%number;
imgrdn4 = (imgrdn3+1)%number;

document.write(image[imgrdn1]);
document.write(image[imgrdn2]);
document.write(image[imgrdn3]);
document.write(image[imgrdn4]);

</script>
ciao