200 OK
201 Created
202 Accepted
203 Provisional Information
204 No Content

300 Multiple Choices
301 Moved Permanently
302 Moved Temporarily
303 Method
304 Not Modified 

400 Bad Request - неправильный запрос
401 Authorization Required - ошибка авторизации
402 Payment Required
403 Forbidden - нет доступа
404 Not Found - документ не найден
405 Method Not Allowed
406 None Acceptable
407 Proxy Authentication Required
408 Request Timeout
409 Conflict
410 Gone

500 Internal Server Error - внутренняя ошибка скрипта
501 Not Implemented
502 Bad Gateway
503 Service Unavailable
504 Gateway Timeout