As a bulb user with a free account, you are allowed ten published pages. If you want to publish a new page, but already have ten, you can unpublish a previous page.
Unpublishing a page
1. Open the publish panel within the page you would like to unpublish.
2. Click the UNPUBLISH button in the bottom left hand corner. Now, your page is unpublished.
*the red exclamation point icon means your page is unpublished
Short video on unpublishing a page: