I've set up a SharePoint 2013 web application and site collection with anonymous access. Everything works fine across all the main browsers (IE, Safari, Firefox, Chrome and Opera) using the default master pages and page layouts. Users can access the site without authenticating and the pages display correctly.
However, if I apply a custom Master Page and custom Page Layouts, I encounter two problems. Firstly, all browsers except IE require authentication before loading. How do I prevent this given that the anonymous access settings are all correct?
And secondly, while the user can display the pages if they cancel the authentication dialog box (after three clicks!), the pages don't conform to the master page and page layout settings - everything is left aligned and no images display.
I'm guessing this second issue may be the cause of the first - that there is a permission setting required on the folder in which the custom master page, CSS and Images reside. however I have checked that folder and the permissions are set to 'Read' for everyone, so I'm at a loss.