Got this error while opening a SharePoint site.
Changing custom error to Off it showed the following error
Line 1: <browsers> Line 2: <browser id="Safari2" parentID="Safari1Plus"> Line 3: <controlAdapters>
Data at the root level is invalid. Line 1, position 1.
Deleted the _vti_cnf folder of /App_Browsers/ of the site and everything was back to normal!!!