Served asset /application.css - 304 Not Modified

Hi I am thinking to hide warning that is ”Served asset /application.css - 304 Not Modified”. How can I fix something if I change the settings? I've run that is less than

server: rails new myapp cd myapp rake db:migrate rails s

client: http://localhost:3000/books

warning: Started GET "/assets/books.css?body=1" for 127.0.0.1 at 2012-02-26 14:48:35 +0900 Served asset /books.css - 304 Not Modified (5ms)

Started GET "/assets/application.css?body=1" for 127.0.0.1 at 2012-02-26 14:48:35 +0900 Served asset /application.css - 304 Not Modified (4ms)

Started GET "/assets/scaffolds.css?body=1" for 127.0.0.1 at 2012-02-26 14:48:35 +0900 Served asset /scaffolds.css - 304 Not Modified (1ms)

Started GET "/assets/books.js?body=1" for 127.0.0.1 at 2012-02-26 14:48:35 +0900 Served asset /books.js - 304 Not Modified (1ms)

Started GET "/assets/application.js?body=1" for 127.0.0.1 at 2012-02-26 14:48:35 +0900 Served asset /application.js - 304 Not Modified (4ms)

Started GET "/assets/jquery_ujs.js?body=1" for 127.0.0.1 at 2012-02-26 14:48:35 +0900 Served asset /jquery_ujs.js - 304 Not Modified (2ms)

Started GET "/assets/jquery.js?body=1" for 127.0.0.1 at 2012-02-26 14:48:35 +0900 Served asset /jquery.js - 304 Not Modified (2ms)