This is defined based on the page template you apply to your pages. Based on your selection it could be either of the two (or none).
Please let me know if you need further info.
Make Sitefinity work best for you.
Progress, Telerik, Sitefinity and certain product names used herein are trademarks or registered trademarks of Progress Software Corporation and/or one of its subsidiaries or affiliates in the U.S. and/or other countries.