W3C Common Logfile Format
Item Description
remotehost Remote hostname (or IP number if DNS hostname is not available, or if DNSLookup is set to off).
rfc931 The remote logname of the user (typically not used).
authuser The username as which the user has authenticated himself.
[date] Date and time of the request.
"request" The request line exactly as it came from the client (typically HEAD, GET or POST followed by the requested URL). followed by the HTTP version in which the response is requested.
status The HTTP status code returned to the client in response to the request.
bytes The content-length of the document transferred.

Extended Logfile Format

Item Description
referrer The URL of the web page that had the link to the page being requested.
process time Time taken to serve the request, in seconds.
browser Browser type (Netscape, MSIE, etc.) and version making the request.
OS Operating system (Windows, Macintosh, Linux, etc.) and version making the request.

Source: W3C, Logging Control In W3C httpd.