Today I went to log into a clients staging site and received the following error ‘Cannot redirect after HTTP headers have been sent.’ from the YSOD (Yellow Screen Of Death). This error has always proven to be a red herring in the past so I always approach it with a fair amount of doubt that the cause is actually related to the exception message. After a little inspection the cause of today’s instance of this error was actually that the databases transaction log was full. After truncating the transaction log all was well again. A couple of other causes I have seen for this exception that are seemingly unrelated are lack of disk or database free space as well as component licensing messages. So if you receive this message seemingly out of the blue I would start by checking the things I mentioned above.