I need to centre a banner rotator code please

[gemmk1]

I need to centre the banner code ive tried adding the <centre></centre> but cant do it.It is a banner roatator code it sits to the left of my forum.I tried the banner rotator mods but could not get them working.This works it just does not sit to the centre

Here is the code thank you

<script>
// Courtesy of SimplytheBest.net - http://simplythebest.net/scripts/
function create() {
        this.width = ''
        this.height = ''
        this.src = ''
        this.href = ''
        this.border = ''
        this.mouseover = ''
        this.sponsor = ''
}
ads = new Array()
for(var i=1; i<=5; i++) { ads[i] = new create() }

ads[1].width = "468"
ads[1].height = "60"
ads[1].src = "http://209.85.12.237/30111/6/0/f5128781/GDAdsBanner.gif"
ads[1].href = "http://gdforum.net"
ads[1].border = "0"
ads[1].mouseover = "Click here to enter the gd forum"
ads[1].sponsor = "best general chat forum around"

ads[2].width = "468"
ads[2].height = "60"
ads[2].src = "http://209.85.12.237/30111/6/0/f5144304/s2f3.png"
ads[2].href = "http://s2fpromotion.co.uk"
ads[2].border = "0"
ads[2].mouseover = "s2f promotion"
ads[2].sponsor = "best free promotion website around"

ads[3].width = "287"
ads[3].height = "60"
ads[3].src = "http://simplythebest.net/images/stbnetmain.gif"
ads[3].href = "http://simplythebest.net"
ads[3].border = "0"
ads[3].mouseover = "Do we need to say more?"
ads[3].sponsor = "Simply the Best"

ads[4].width = "468"
ads[4].height = "60"
ads[4].src = "http://i42.photobucket.com/albums/e303/jlmf/logo-2.gif"
ads[4].href = "http://strangers2friends.co.uk"
ads[4].border = "0"
ads[4].mouseover = "friendship and support forum"
ads[4].sponsor = "strangers 2 friends"



var n = Math.random() + ''
n = parseInt(n.charAt(5))
if(n >5) {
        n = n - 5
}
else if(n==0) {
        n = n + 5
}
n += ""

var image = ads[n]
var ad = ""
ad += '<a href="' + image.href + '" \n'
ad += 'onMouseOver="self.status=\'' + image.mouseover + '\'\;return true" \n'
ad += 'onMouseOut="self.status=\'\'"> \n'
ad += '<img src="' + image.src + '" width=' + image.width
ad += '\n height=' + image.height + ' border=' + image.border
ad += '\n><br>Please visit our sponsor: ' + image.sponsor + '</a>'
</script>




<script language="JavaScript">
<!-- hiding this script
document.write(ad)
// -->
</script>

Thank you in advance