Intermittent forbidden errors (403)

After applying a new master page and related theme components, we have been receiving reports that users were being presented with 403 ‘forbidden’ errors when trying to load our intranet site. After refreshing the screen four (4) times, the page would finally load.

I checked the web server’s Application log and found that every time a user received a 403 error, there was an “Information” Web Event message logged with a source of ASP.NET and an ID of ID 1314. The body of the event included, among other information:

Event code: 4011
Event message: An unhandled access exception has occurred.

After doing research and knowing this was most likely a security issue, I came around to fixing permissions on the Bin and _app_bin folders for the IIS virtual server that was hosting my SharePoint Web Application. I added the server’s local group “users” (which includes the domain group users) to both folders with READ permissions.

After an application pool restart, there have been no more reports of 403 errors and not a single 1314 report has been shown in the Application log.