Sharepoint - User with Full Control Permission is getting Access Denied Message
Solved!
Though I'm still not certain why it occurred on this site and on no others...
I simply had to provide global read access to the master page library. Site actions > site settings > Master Page and page layouts > Library tab > Permissions. Add All authenticated users to READ ONLY.
The scope of your problem may range between the ones that are mentioned below. Have them carefully checked.
Master page or the Page Layout used by the home page are being checked out by Site Collection Admin or is lying in "pending" approval state.
Any custom solution that might be added in the landing page can cause access issues. Verify closely the uls logs for this.
Incorrect configuration of Object cache reader account renders access denied to everyone including application pool identity account let alone your site collection admins and owners. See the Full read and Full read + write are correctly implemented incase object cache reader is configured.
Permission level policy at the web application levels have changed or incorrectly modified. If this is the cause, verify that the issue persists in any other site collection within the same web application.
The permissions of the homepage or the page the user is trying to edit of the site collection or the document library where the homepage resides has the correct permissions.
Try to go through the ULS logs incase the issue occurs outside the scope of the above mentioned.
if your site is a publishing site and you want people with read permission to see draft pages, you should make sure that these pages have been published at least once before.