I have a custom master page, custom.master, for a publishing site. It was working fine, however I just enabled anonymous access to the publishing site, and now browsing to the home page for that site brings up the following error:
Cannot find ContentPlaceHolder 'PlaceHolderTopBanner' in the master page '/_catalogs/masterpage/custom.master', verify content control's ContentPlaceHolderID attribute in the content page.
I started from a minimal master page for custom.master. PlaceHolderTopBanner is a custom ContentPlaceHolder that I created (as an area for a different banner image to go on each page.)
If I disable anonymous access again, forcing me to log in before accessing the page, there are no errors and the page loads fine.
To enable anonymous access I enabled it at the web application level, and then for the publishing site -- I chose anonymous access for 'entire site'.
I guess it must be a permissions thing, but I have no clue as to what! Any help appreciated.