<script language="JavaScript">
<!--
// Create arrays to contain all the values 
// for links and image locations
link = new Array
image = new Array
 
link[1]="http://www.wildexpo.com.au/Aust%20Rep%20Show/"
image[1]="http://www.reptilesaustralia.com.au/forums/Ads/wildexpo.gif"
 
link[2]="http://www.excite.com"
image[2]="http://www.excite.com/mesp/images/excite/new_logo-180.gif"
 
link[3]="http://www.lycos.com"
image[3]="http://a284.g.akamai.net/7/284/987/000/lygo.com/ly/i/lyguide.gif"
 
link[4]="http://www.cnet.com"
image[4]="http://cnet.com/Images/Headers/cnet-1-title.gif"
 
link[5]="http://www.webcrawler.com"
image[5]="http://webcrawler.com/img/web/hdr/home_header.gif"
 
 
// Create a random number between 1 and five
random_num = (Math.round((Math.random()*4)+1))
 
 
// Write a link and images with random array
document.write("<a href=\"" + link[random_num] + "\">");
document.write("<img src=\"" + image[random_num] + "\" border=\"0\"></a>");
 
-->
</script>

document.write("<a href=\"" + link[random_num] + "\">");

document.write("<a href=\"" + link[random_num] + "\" target=\"_blank\">");

document.write("<a href=\"" + link[random_num] + "\" target=\"_blank\">");
 
document.write("<img src=\"" + image[random_num] + "\" border=\"0\"></a>");

document.write("<a href=\\"" + link[random_num] + "\\" target=\\"_blank\\">");
document.write("<img src=\\"" + image[random_num] + "\\" border=\\"0\\"></a>");

(double backslash should be escaped to backslash by your board software which can then go on to be the javascript escape character when the page is rendered)

document.write('<a href="' + link[random_num] + '" target="_blank">');
document.write('<img src="' + image[random_num] + '" border="0"></a>');

(all literal strings in the Javascript are quoted with single quote characters, and attributes in the dynamically created elements are quoted with double quote characters :- escaping doesn't matter)