Refer to this section "Integrate Style into the Experience Manager template "-- Adobe Experience Manager Help | Creating an Adobe Experience Manager 6.4 website using Editable Templates
Look at this artilce - notice how we add CSS in a clientlibs. You can control that appearance of your site by using CSS like we show in this article:Adobe Experience Manager Help | Creating an Adobe Experience Manager 6.4 website using Editable Templates
The document states the service pack required for AEM 6.3. Also - more information about this subject in this session of Ask the AEM community experts -- AEM Content Services: What, Why, and How?
Reason why that was asked was becasue we can tell if issue is with your project or something is corrupt on the system. If it successfully works in a DEV sandbox instance - then we know its not something specific to your project. You should be able to deploy your project as a package and deploy very ...