diff --git a/collects/scribble/scribble-common.js b/collects/scribble/scribble-common.js
index c42b58aa..97cd0388 100644
--- a/collects/scribble/scribble-common.js
+++ b/collects/scribble/scribble-common.js
@@ -19,15 +19,25 @@ function SetCookie(key, val) {
     key + "=" + escape(val) + "; expires="+ d.toGMTString() + "; path=/";
 }
 
-function GotoPLTRoot() {
-  var u = GetCookie("PLT_Root");
+function GotoPLTRoot(ver) {
+  var u = GetCookie("PLT_Root."+ver);
   if (u == null) return true; // no cookie: use plain up link
   location = u;
   return false;
 }
 
-function SetPLTRoot() {
-  SetCookie("PLT_Root", location);
+function SetPLTRoot(ver, relative) {
+  var root = location.protocol + "//" + location.host
+           + NormalizePath(location.pathname.replace(/[^\/]*$/, relative));
+  SetCookie("PLT_Root."+ver, root);
+}
+
+normalize_rxs = [/\/\/+/g, /\/\.(\/|$)/, /\/[^\/]*\/\.\.(\/|$)/];
+function NormalizePath(path) {
+  var tmp, i;
+  for (i = 0; i < normalize_rxs.length; i++)
+    while ((tmp = path.replace(normalize_rxs[i], "/")) != path) path = tmp;
+  return path;
 }
 
 function DoSearchKey(event, field) {