function showOxygenAd(){
                var str = document.location.pathname;
                var keywords=new Array("css", "xsl","nvdl","docbook","relaxng","xml");
                var image;
                    
                    for (i=0;i<keywords.length;i++) {
                        
                        var keywordLength = keywords[i].length + 1;
                        var element = str.substring(1, keywordLength);
                        
                        if (keywords[i] == element){
                            image = "oxygenxml_" + keywords[i] + ".gif"; 
                        }
                    }

                    if  (image == null) {
                        // default image
                        image = "Banner728x90_oxygenxml.gif";
                    }    
                    
        return document.write("<a href='http://www.oxygenxml.com/?av=3144&sh=200086293'><img src='/oxygen/" + image + "' border='0'/></a><br />");
}