UPDATE: There is a gem jquery-ui-themes perfectly fix this, recommend to use this gem.

The following will fix the jQuery-ui theme’s issue on Rails 3.1, tested in production

1. Add this line to app/assets/stylesheets/application.css

    *= require vendor
   

2. create vendor/assets/stylesheets/vendor.css with

    /*
    *= require_tree ./jquery_ui 
    *
    */
   

3. Put the jQuery-ui in vendor folder

    vendor
      └── assets
            └── stylesheets
                 ├── images
                 │   ├── ui-bg_flat_0_aaaaaa_40x100.png
                 │   ├── ...
                 ├── jquery_ui
                 │   └── jquery-ui-1.8.16.custom.css
                 └── vendor.css
   

The ugly way, but it just worked.