diff --git a/railties/Rakefile b/railties/Rakefile
index daffd8ce30..efdb31cbd8 100644
--- a/railties/Rakefile
+++ b/railties/Rakefile
@@ -50,6 +50,12 @@ task :update_prototype_ujs do
   system "curl http://github.com/rails/prototype-ujs/raw/master/src/rails.js > lib/rails/generators/rails/app/templates/public/javascripts/rails.js"
 end
 
+# Validate guides -------------------------------------------------------------------------
+desc 'Validate guides, use ONLY=foo to process just "foo.html"'
+task :validate_guides do
+  ruby "guides/w3c_validator.rb"
+end
+
 # Generate documentation ------------------------------------------------------------------
 
 Rake::RDocTask.new { |rdoc|
diff --git a/railties/guides/w3c_validator.rb b/railties/guides/w3c_validator.rb
new file mode 100644
index 0000000000..b55645a7a9
--- /dev/null
+++ b/railties/guides/w3c_validator.rb
@@ -0,0 +1,67 @@
+# ---------------------------------------------------------------------------
+#
+# This script validates the generated guides against the W3C Validator.
+#
+# Guides are taken from the output directory, from where all .html files are
+# submitted to the validator.
+#
+# This script is prepared to be launched from the railties directory as a rake task:
+#
+# rake validate_guides
+#
+# If nothing is specified, all files will be validated, but you can check just
+# some of them using this environment variable:
+#
+#   ONLY
+#     Use ONLY if you want to validate only one or a set of guides. Prefixes are
+#     enough:
+#
+#       # validates only association_basics.html
+#       ONLY=assoc rake validate_guides
+#
+#     Separate many using commas:
+#
+#       # validates only 
+#       ONLY=assoc,migrations rake validate_guides
+#
+# ---------------------------------------------------------------------------
+
+require 'rubygems'
+require 'w3c_validators'
+include W3CValidators
+
+module RailsGuides
+  class Validator
+    
+    def validate
+      validator = MarkupValidator.new
+
+      guides_to_validate.each do |f|  
+        puts "Validating #{f}"
+        results = validator.validate_file(f)
+
+        if !results.validity
+          puts "#{f} FAILED W3C validation with #{results.errors.size} error(s):"
+          results.errors.each do |error|
+            puts error.to_s
+          end
+        end
+      end
+    end
+    
+    private
+    def guides_to_validate
+      guides = Dir["./guides/output/*.html"]
+      ENV.key?('ONLY') ? select_only(guides) : guides
+    end
+
+    def select_only(guides)
+      prefixes = ENV['ONLY'].split(",").map(&:strip)
+      guides.select do |guide|
+        prefixes.any? {|p| guide.start_with?("./guides/output/#{p}")}
+      end
+    end
+  end
+end
+
+RailsGuides::Validator.new.validate
\ No newline at end of file