diff --git a/.gitignore b/.gitignore
index 0e0e7ce..fbfb620 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,3 +20,4 @@ bundle
 coverage
 *#
 .ruby-version
+NOTES
diff --git a/README.md b/README.md
index f908972..48f0e73 100644
--- a/README.md
+++ b/README.md
@@ -88,6 +88,19 @@ Deployment
 ----------
 See [notes on deployment](docs/deployment.md)
 
+Notice Grouping
+---------------
+The way Errbit arranges notices into error groups is configurable. By default,
+Errbit uses the notice's error class, error message, complete backtrace,
+component (or controller), action and environment name to generate a unique
+fingerprint for every notice. Notices with identical fingerprints appear in the
+UI as different occurences of the same error and notices with differing
+fingerprints are displayed as separate errors.
+
+Changing the fingerprinter (under the 'config' menu) applies to all apps and
+the change affects only notices that arrive after the change. If you want to
+refingerprint old notices, you can run `rake errbit:notice_refingerprint`.
+
 Authentication
 --------------
 ### Configuring GitHub authentication:
--
libgit2 0.21.2