+404 RESPONSES
+-------------
+
+Any of the following cases will result in a 404 response being sent to
+the client.
+
+ * Failure of the mapping procedure to find a matching physical file.
+ * Presence of a path element during mapping that begins with a dot.
+ * A path element which, after URL unescaping, contains slashes.
+ * The mapping procedure finding a file which is neither a directory
+ nor a regular file.
+ * Presence of a non-final but empty path element during mapping.
+ * A physical file having been found which is not being matched by any
+ *match* stanza.
+
+*dirplex* will send a built-in 404 response by default, but any
+`.htrc` file or global configuration may define a request handler
+named `.notfound` to customize the behavior. Note that, unlike
+successful requests, such a handler will not be passed the
+`X-Ash-File` header.
+
+The built-in `.notfound` handler can also be used in *match* or
+*capture* stanzas.