[рони]

samdo,
попробуйте так, копировать целиком

<script>
function enRu() {
   var x = window.location+"";
   var reg = /\/en\//;
   if(reg.test(x)) x = x.replace(reg,"/");
   else {
   var n = x.lastIndexOf("/");
   x = x.slice(0,n) + "/en" + x.slice(n)
   }
   window.location = x
}

  </script>
<a href="#" onclick="return enRu()">English/Russian</a>