diff -ru cliki_0.4.3/cliki-instance.lisp cliki_0.4.3-diff/cliki-instance.lisp
--- cliki_0.4.3/cliki-instance.lisp	Mon May 10 12:26:20 2004
+++ cliki_0.4.3-diff/cliki-instance.lisp	Thu Feb 24 00:37:51 2005
@@ -188,6 +188,10 @@
 	       (merge-url (parse-urlstring "http://ww.telent.net/cclan/")
 			  (caar d)))
 	      t)))
+	 ((url-query-param u "diff")
+	  (view-page-diff handler request page title
+			  (integer-for (car (url-query-param u "va")))
+			  (integer-for (car (url-query-param u "vb")))))
 	 (t
 	  (view-page handler request page title :version version)))))))
 
diff -ru cliki_0.4.3/cliki.asd cliki_0.4.3-diff/cliki.asd
--- cliki_0.4.3/cliki.asd	Mon May 10 05:55:11 2004
+++ cliki_0.4.3-diff/cliki.asd	Thu Feb 24 11:31:33 2005
@@ -3,7 +3,7 @@
 (in-package :cliki-system)
 
 (defsystem cliki
-  :depends-on (ARANEIDA net-telent-date xmls)
+  :depends-on (ARANEIDA net-telent-date xmls cl-html-diff)
   :version "0.4.3"
   :components ((:file "defpackage")               
 	       (:file "utilities" :depends-on ("defpackage"))
diff -ru cliki_0.4.3/view.lisp cliki_0.4.3-diff/view.lisp
--- cliki_0.4.3/view.lisp	Mon May 10 12:26:20 2004
+++ cliki_0.4.3-diff/view.lisp	Thu Feb 24 11:39:18 2005
@@ -51,22 +51,39 @@
 		 :default (car (page-versions page)))))
 
 (defun version-links (cliki page request)
-  (let ((ver (request-for-version page request)))
-    (loop for v in (reverse
-		    (subseq (page-versions page) 
-			    0 (min 5 (length (page-versions page)))))
-	  if (= ver v)
-	  collect `((b :title 
-		       ,(universal-time-to-http-date
-			 (file-write-date (page-pathname page :version ver))))
-		    ,ver)
-	  else
-	  collect `((a :href ,(format nil "~A?v=~A" 
-				      (urlstring (page-url cliki page))  v)
-		       :title 
-		       ,(universal-time-to-http-date
-			 (file-write-date (page-pathname page :version v))))
-		    ,v))))
+  (let ((ver (request-for-version page request))
+	(recent-versions (reverse
+			  (subseq (page-versions page) 
+				  0 (min 5 (length (page-versions page)))))))
+    (let ((links '()))
+      (do ((versions recent-versions (cdr versions))
+	   (next-versions (cdr recent-versions) (cdr next-versions)))
+	  ((endp versions) (reverse links))
+	(let ((v (car versions))
+	      (next-v (car next-versions)))
+	  (if (= ver v)
+	      (push `((b :title 
+			 ,(universal-time-to-http-date
+			   (file-write-date (page-pathname page :version ver))))
+		      ,ver)
+		    links)
+	      (push `((a :href ,(format nil "~A?v=~A" 
+					(urlstring (page-url cliki page))  v)
+			 :title 
+			 ,(universal-time-to-http-date
+			   (file-write-date (page-pathname page :version v))))
+		      ,v)
+		    links))
+	  (when next-v
+	      (push `((a :href ,(format nil "~A?diff&va=~A&vb=~A"
+					(urlstring (page-url cliki page))
+					v
+					next-v)
+			 :title ,(format nil "Highlight differences between versions ~A and ~A"
+					 v next-v))
+		      "<")
+		    links)))))))
+
   
 (defmethod cliki-page-footer
     ((cliki cliki-view) request title)
@@ -194,6 +211,50 @@
 	  (format out
 		  "This page doesn't exist yet.  Please create it if you want to"))))
 
+  t)
+
+
+(defun page-contents (cliki page &key (version :newest))
+  (with-output-to-string (s)
+    (cliki::write-page-contents-to-stream cliki page s :version version)))
+
+(defun diff-page-versions (cliki page version1 version2)
+  (let ((a (page-contents cliki page :version version1))
+	(b (page-contents cliki page :version version2)))
+    (html-diff:html-diff a b)))
+
+(defun view-page-diff (cliki request page title version1 version2)
+  (request-send-headers request)
+  (with-page-surround (cliki
+		       request
+		       title
+		       '(((META :NAME "ROBOTS" :CONTENT "NOFOLLOW"))))
+    (if page
+	(progn
+	  (let* ((topics 
+		  (sort (delete page (copy-list (page-topics page)))
+			#'string-lessp
+			:key #'page-title))
+		 (backlinks
+		  (sort (set-difference
+			 (delete page (copy-list (page-backlinks page)))
+			 topics)
+			#'string-lessp :key #'page-title)))
+	    (format out "~A" (diff-page-versions cliki page version1 version2))
+	    (when topics
+	      (format out "<hr><p><b>Page~p in this topic: </b> "
+		      (length topics))
+	      (dolist (c topics)
+		(format out "~A &nbsp; "
+			(write-a-href cliki (page-title c) nil))))
+	    (when backlinks
+	      (format out "<hr><p><b>~A linked from: </b> "
+		      (if topics "Also" "This page is"))
+	      (dolist (c backlinks)
+		(format out "~A &nbsp; "
+			(write-a-href cliki (page-title c) nil))))))
+	(format out
+		"This page doesn't exist yet.  Please create it if you want to")))
   t)