http://edgeguides.rubyonrails.org/asset_pipeline.html#precompiling-assets中

When using asset precompilation (the production default), you will need to ensure that your controller assets will be precompiled when loading them on a per page basis. By default .coffee and .scss files will not be precompiled on their own. This will result in false positives during development as these files will work just fine since assets will be compiled on the fly. When running in production however, you will see 500 errors since live compilation is turned off by default.

这几句该怎么理解啊，不懂求教。