Media queries only applied for authenticated users
As Molot commented it is just a cache problem. You need to clear your browser cache to get the updated css. Another trick that works for me is to add a query string in the URL (e.g http://example.com/node/test?awy). You may need to turn off the css aggregation under Performance page to make sure that you will get the updated css and not the cached copy.

You can use Drush to clear your cache by using drush cc all.