Visualforce: Lightning Experience Readiness and Styling

Use Visualforce to develop custom pages for your org. In this release, changes are focused on making it easier to use Visualforce pages seamlessly in Lightning Experience. This change applies to Lightning Experience, Salesforce Classic, and all versions of the Salesforce app.
Available in: Salesforce Classic and Lightning Experience
Available in: Contact Manager, Group, Professional, Enterprise, Performance, Unlimited, and Developer Editions

For more information on features affected by these enhancements, refer to the Visualforce Developer Guide.