Random banner only displaying the first image

function random_imglink(){
var myimages=new Array()
myimages[1]="http://sevir.sitegoz.com/jchs/Banner1.png"
myimages[2]="http://sevir.sitegoz.com/jchs/banner2.png"
myimages[3]="http://sevir.sitegoz.com/jchs/banner3.png"
myimages[4]="http://sevir.sitegoz.com/jchs/banner4.png"
myimages[5]="http://sevir.sitegoz.com/jchs/banner5.png"
myimages[6]="http://sevir.sitegoz.com/jchs/banner6.png"

var ry=Math.floor(Math.random()*myimages.length)
if (ry==0)
ry=1
document.write('<img src="'+myimages[ry]+'" border=0>')
}

<script language="JavaScript">
<!--
random_imglink()
//-->
</script>