var imgHeight = 73;
var imgWidth = 557;

function create() {
        this.src = ''
}
ads = new Array()
for(var i=1; i<=5; i++) { ads[i] = new create() }

ads[1].src = "_images/banner1.jpg"
ads[2].src = "_images/banner2.jpg"
ads[3].src = "_images/banner3.jpg"
ads[4].src = "_images/banner4.jpg"
ads[5].src = "_images/banner5.jpg"

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 += '<img src="' + image.src + '" width=' + imgWidth
ad += '\n height=' + imgHeight + ' border=0>'