more informative 404 page for project server

server-routes.rkt

@@ -253,6 +253,9 @@
 ;; 404 route
 (define/contract (route-404 req)
   (request? . -> . response?)
-  (define error-text (format "route-404: Can't find ~a" (->string (req->path req))))
-  (message error-text)
-  (response/xexpr+doctype `(html ,error-text)))
+  (define missing-path (->string (req->path req)))
+  (message (format "route-404: Can't find ~a" missing-path))
+  (response/xexpr+doctype
+   `(html 
+     (head (title "404 error") (link ((href "/error.css") (rel "stylesheet"))))
+     (body (div ((class "section")) (div ((class "title")) "404 error") (p ,(format "~v" missing-path) " was not found"))))))