function mkLink (url, label, target, extra) {
   if (!extra) { extra=''; }
   if (!target) { target='_self'; }
   if (url.indexOf("http://")==-1) { url ="http://"+url; }
   document.write('<a href="' + url + '" target="'+ target + '" '  +  extra  + '>'+label+'</a>') ;
}