Error:- ActionView::Template::Errror (application.css isn’t precompiled)

Rails assumes that you have your files pre-compiled in the production environment.

if want to compile at runtime set as the following

in the file config/environments/production.rb

config.assets.compile = true

for better performance in production want to set config.assets.compile to false in production.rb

You can precompile with this rake task:

bundle exec rake assets:precompile