diff --git a/Makefile b/Makefile
index e5a2ee5..28c1c2e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,22 +1,40 @@
-OUTPUT_DIR = public
+# Hugo configuration.
+HUGO_COMMAND := hugo
+HUGO_OPTIONS := --i18n-warnings
 
-SSH_HOST = www.cosin.ch
-SSH_USER = root
-TARGET_DIR = /srv/www/www.cosin.ch/
+OUTPUT_DIR := public
 
-HUGO_FLAGS = --i18n-warnings
+# Vnu validator configuration.
+VNU_COMMAND := vnu
+VNU_OPTIONS := --skip-non-html --also-check-css
 
-.PHONY: generate server upload clean
+# Rsync deployment configuration.
+SSH_HOST := www.cosin.ch
+SSH_USER := root
+TARGET_DIR := /srv/www/www.cosin.ch/
 
+# Non-file goals.
+.PHONY: server generate validate upload clean
 
-generate:
-	hugo $(HUGO_FLAGS)
+# Include the configuration files.
+-include config.mk settings.mk
 
+# Start a local development server.
 server:
-	hugo $(HUGO_FLAGS) server
+	hugo $(HUGO_OPTIONS) server
 
+# Generate static output files for deployment.
+generate:
+	hugo $(HUGO_OPTIONS)
+
+# Validate html and css in generated files.
+validate: generate
+	$(VNU_COMMAND) $(VNU_OPTIONS) $(OUTPUT_DIR)
+
+# Deploy the website to the production webserver.
 upload: generate
-	rsync -P -rvzc --delete --include=*/fahrplan/ --exclude=fahrplan/ $(OUTPUT_DIR)/ $(SSH_USER)@$(SSH_HOST):$(TARGET_DIR)
+	rsync --rsh=ssh -P -rvzc --cvs-exclude --delete --include=*/fahrplan/ --exclude=fahrplan/ $(OUTPUT_DIR)/ $(SSH_USER)@$(SSH_HOST):$(TARGET_DIR)
 
+# Clean up.
 clean:
 	rm -rf $(OUTPUT_DIR)