Regardless of what modules are compiled and used, Apache as a basic web server complies with the following IETF recommendations:

RFC 1945 (Informational)

The Hypertext Transfer Protocol (HTTP) is an application-level protocol with the lightness and speed necessary for distributed, collaborative, hypermedia information systems. This documents HTTP/1.0.

RFC 2616 (Standards Track)

The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. This documents HTTP/1.1.

RFC 2396 (Standards Track)

A Uniform Resource Identifier (URI) is a compact string of characters for identifying an abstract or physical resource.

RFC 4346 (Standards Track)

The TLS protocol provides communications security over the Internet. It provides encryption, and is designed to prevent eavesdropping, tampering, and message forgery.

Regarding the Hypertext Markup Language, Apache complies with the following IETF and W3C recommendations:

RFC 2854 (Informational)

This document summarizes the history of HTML development, and defines the "text/html" MIME type by pointing to the relevant W3C recommendations.

HTML 4.01 Specification (Errata)

This specification defines the HyperText Markup Language (HTML), the publishing language of the World Wide Web. This specification defines HTML 4.01, which is a subversion of HTML 4.

HTML 3.2 Reference Specification

The HyperText Markup Language (HTML) is a simple markup language used to create hypertext documents that are portable from one platform to another. HTML documents are SGML documents.

XHTML 1.1 - Module-based XHTML (Errata)

This Recommendation defines a new XHTML document type that is based upon the module framework and modules defined in Modularization of XHTML.

XHTML 1.0 The Extensible HyperText Markup Language (Second Edition) (Errata)

This specification defines the Second Edition of XHTML 1.0, a reformulation of HTML 4 as an XML 1.0 application, and three DTDs corresponding to the ones defined by HTML 4.

Concerning the different methods of authentication, Apache follows the following IETF recommendations:

RFC 2617 (Standards Track)

"HTTP/1.0", includes the specification for a Basic Access Authentication scheme.

The following links document ISO and other language and country code information:

ISO 639-2

ISO 639 provides two sets of language codes, one as a two-letter code set (639-1) and another as a three-letter code set (this part of ISO 639) for the representation of names of languages.

ISO 3166-1

These pages document the country names (official short names in English) in alphabetical order as given in ISO 3166-1 and the corresponding ISO 3166-1-alpha-2 code elements.

BCP 47 (Best Current Practice), RFC 3066

This document describes a language tag for use in cases where it is desired to indicate the language used in an information object, how to register values for use in this language tag, and a construct for matching such language tags.

RFC 3282 (Standards Track)

This document defines a "Content-language:" header, for use in cases where one desires to indicate the language of something that has RFC 822-like headers, like MIME body parts or Web documents, and an "Accept-Language:" header for use in cases where one wishes to indicate one's preferences with regard to language.