Confusion related when deploy to heroku

I am using Ruby1.9.3 and Rails3.2 version. I am developing sample_app by
using Michael hartl’s book.

I get message for Javascript and CSS after using “rails s” like

When I use code “rails s”, and then I got error like:

Served asset /sessions.js - 304 Not Modified (1ms)

[2014-05-21 17:58:58] WARN Could not determine content-length of
response body. Set content-length of the response or set
Response#chunked = true

After this error, I changed code in development.rb file from
config.assets.debug = true


config.assets.debug = false.

Now my question is, Will anything go wrong when I deploy to heroku as i
changed code in development.rb file. My application will work correctly?

Yes, It should work correctly as this change will not effect your heroku