From the NLM Technical Bulletin:
PMC (formerly known as PubMed Central) has shortened its name in order to avoid confusion with PubMed. What’s also new is PMC’s look and feel, which has been updated to conform to NCBI’s new standards for page design. This redesign allows for a cleaner and more uniform presentation across PMC’s site as well as its article, issue and journal archive pages.
The NLM Tech Bulletin post also includes six screen caps that highlight the changes to the web site.