You were able to view these pages at one time. I cannot find them any longer
Here is some information about Campaigns. Unfortunately, they do come and go. Some of them become "permanent" like the calendar but others are only accessible for a short time. This article gives more information about how you might find what you are looking for.
We are sorry we cannot be of more help.
Many of the campaigns become discovery activities and can be found under the tab "Activities" and then "All Activities". Here is the direct URL: https://www.familysearch.org/discovery/
Is there a specific campaign you are looking for - I may be able to find it if it still exists?