A website that lets you quickly lookup any Apple API error. OSStatus.com lets you search by error name, integer, OSType, hex or string code, framework name or header file. Search results give you platform (OS X or iOS), framework, header file, error name, code and description, making it easy to identify any cryptic errors you're experiencing. OSStatus.com is much faster than digging through the Apple documentation or header files yourself so it's definitely worth bookmarking.