invalid css on rails app Michael Hartl tutorial - heroku

Question

I just finished chapter five of the Mike Hartle rails tutorial and was a little confused when I loaded my files to heroku and the css for whatever reason was not working its magic like it was for me localy. Here is a copy of my heroku logs if that helps at all.
2013-09-17T00:40:31.225391+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/activesupport-4.0.0/lib/active_support/tagged_logging.rb:25:in `tagged'
2013-09-17T00:40:31.225544+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/actionpack-4.0.0/lib/action_dispatch/middleware/static.rb:64:in `call'
2013-09-17T00:40:31.225544+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/rack-1.5.2/lib/rack/content_length.rb:14:in `call'
2013-09-17T00:40:31.225544+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/rack-1.5.2/lib/rack/handler/webrick.rb:60:in `service'
2013-09-17T00:40:31.359182+00:00 heroku[router]: at=info method=GET path=/favicon.ico host=fathomless-earth-8911.herokuapp.com fwd="66.235.48.7" dyno=web.1 connect=1ms service=4ms status=304 bytes=0
2013-09-17T00:40:31.225689+00:00 app[web.1]:
2013-09-17T00:40:31.225689+00:00 app[web.1]:
2013-09-17T00:40:31.225689+00:00 app[web.1]: ActionController::RoutingError (No route matches [GET] "/images/rails.png"):
2013-09-17T00:40:31.225689+00:00 app[web.1]:
2013-09-17T00:40:31.225689+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/railties-4.0.0/lib/rails/rack/logger.rb:38:in `call_app'
2013-09-17T00:40:31.226038+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/railties-4.0.0/lib/rails/rack/logger.rb:21:in `block in call'
2013-09-17T00:40:31.225689+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/actionpack-4.0.0/lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
2013-09-17T00:40:31.226038+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/activesupport-4.0.0/lib/active_support/tagged_logging.rb:67:in `block in tagged'
2013-09-17T00:40:31.225689+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/actionpack-4.0.0/lib/action_dispatch/middleware/debug_exceptions.rb:21:in `call'
2013-09-17T00:40:31.226038+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/rack-1.5.2/lib/rack/methodoverride.rb:21:in `call'
2013-09-17T00:40:31.226038+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/actionpack-4.0.0/lib/action_dispatch/middleware/request_id.rb:21:in `call'
2013-09-17T00:40:31.226038+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/activesupport-4.0.0/lib/active_support/cache/strategy/local_cache.rb:83:in `call'
2013-09-17T00:40:31.226038+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/railties-4.0.0/lib/rails/rack/logger.rb:21:in `call'
2013-09-17T00:40:31.226038+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/activesupport-4.0.0/lib/active_support/tagged_logging.rb:67:in `tagged'
2013-09-17T00:40:31.226038+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/activesupport-4.0.0/lib/active_support/tagged_logging.rb:25:in `tagged'
2013-09-17T00:40:31.226188+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/rack-1.5.2/lib/rack/lock.rb:17:in `call'
2013-09-17T00:40:31.226188+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/rack-1.5.2/lib/rack/content_length.rb:14:in `call'
2013-09-17T00:40:31.226188+00:00 app[web.1]:
2013-09-17T00:40:31.226188+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/railties-4.0.0/lib/rails/engine.rb:511:in `call'
2013-09-17T00:40:31.226188+00:00 app[web.1]: vendor/ruby-2.0.0/lib/ruby/2.0.0/webrick/httpserver.rb:94:in `run'
2013-09-17T00:40:31.226188+00:00 app[web.1]:
2013-09-17T00:40:31.226188+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/railties-4.0.0/lib/rails/application.rb:97:in `call'
2013-09-17T00:40:31.226038+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/actionpack-4.0.0/lib/action_dispatch/middleware/static.rb:64:in `call'
2013-09-17T00:40:31.226038+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/rack-1.5.2/lib/rack/runtime.rb:17:in `call'
2013-09-17T00:40:31.226188+00:00 app[web.1]: vendor/ruby-2.0.0/lib/ruby/2.0.0/webrick/httpserver.rb:138:in `service'
2013-09-17T00:40:31.226188+00:00 app[web.1]: vendor/ruby-2.0.0/lib/ruby/2.0.0/webrick/server.rb:295:in `block in start_thread'
2013-09-17T00:40:31.226188+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/rack-1.5.2/lib/rack/handler/webrick.rb:60:in `service'

Answer 1

I ran into the same issue (using Windows 7). I found that the question was only partially answered by Heijmans above. Hartl isn't very specific about why or how this error occurs but does address the issue in section 2.3.5 and the end of the intro to Chapter 3.
Mine worked after the following process.
First, I ran
> heroku run bundle exec rake assets:precompile
> heroku open
But I still got errors. Then I followed Hartl's suggestion in the book in the following manner.
> git add .
> git commit -m "Add precompiled assets for Heroku"
> git push
> git push heroku master
> heroku run rake db:migrate
> heroku open
Interestingly, Hartl states that "This shouldn’t be necessary, and I have been unable to reproduce the issue, but the reports are common enough that I include it here for reference."
[tag: heroku]
[tag: railstutorial.org]
[tag: Windows 7]
[tag: Rails 4]

Answer 2

In Production the asset pipeline will kick in and your app will look for the precompiled version of the assets. I'm not familiar with that tutorial but I am assuming because this is the leading cause of css and javascript not available in production (heroku). There are 2 ways you can fix this...
The first way is to precompile your assets on heroku by running the precompile command from your app's directory:
heroku run bundle exec rake assets:precompile
The second way (not suggested) is to turn of the asset pipeline by commenting these lines out in your config/environments/production.rb file:
# Do not fallback to assets pipeline if a precompiled asset is missed.
# config.assets.compile = false
You may also want to turn off digests for your asset urls if you are disabling your precompiled assets
# Generate digests for assets URLs.
# config.assets.digest = true