title: rake asset:precompile for rails 2.3.18
body: <p>i have deployed a rails application on heroku
  ruby version 1.9.3-p547
  rails version 2.3.18</p>
  
  <p>while i am using webrick server its working properly,but using unicorn server its not working ,that means it didn't support javascript, css and all,it shows error like this</p>
  
  <p>ActionController::RoutingError (No route matches "/images/search.jpg" with {:method=>:get}):</p>
  
  <p>so i have tried this command $ bundle exec rake assets:precompile RAILS_ENV=production RAILS_GROUPS=assets
  but it shows error like this</p>
  
  <p>rake aborted!
  Don't know how to build task 'assets:precompile'</p>
  
  <p>in rails 2.3.18 not even have assets.please help me to solve this.</p>
  
  <p>thanks in advance</p>