You have just updated an asset ( may be image file or script or stylesheet ), committed that and deployed that change to production or staging or qa or uat server.
For example: in case of image asset you have only edited the image may be added an icon in an sprite-image. You see that in browser no icon is rendered. When you inspect the DOM you see the URL is outdated. You know the URL is outdated because you have checked the Asset-precompile manifest
your_app/current/public/assets/manifest-[digest].json in the server which looks like
"radiobutton.png":"radiobutton-7b4ebeb557e1c6f7bd0318dddf8c30a5.png" "rating.png":"rating-b35838ad4f322dac3f7a58af9e23b038.png" "sprite-add.png":"sprite-add-2e3bf15cb765b03fb86c41a9108fd360.png" "sprite-icon.png":"sprite-icon-7e92af7a99b7f6809bb597a257c344cb.png" "sprite.png":"sprite-8cdd1976f591e6588ab579177a6a3f47.png" "star.png":"star-2e08bde0ace01b6cf05ae1334750dd88.png" "tick.png":"tick-c7aeac2132c7dd3e2bbd3e1a3cb0ff00.png"
After you have deployed your rails server might not be restarted or some thing happened and your rails server failed to load new asset-manifest in memory by looking which Rails maps the asset requests.
Deploy your application again
if still not solved
- SSH into the system delete the file
$ bundle exec rake assets:clear
$ bundle exec rake assets:precompile RAILS_ENV=production
- restart the webserver ( for Nginx
/etc/init.d/nginx restart or $ sudo service nginx restart)
- if still not solved deploy your app again