C & G web

HTML's META-tag

META Tag Dictionary

META tags have two possible attributes:
  • <META HTTP-EQUIV="name" CONTENT="content">
  • <META NAME="name" CONTENT="content">

META tags should be placed in the head of the HTML document, between the <HEAD> and </HEAD> tags (especially important in documents using FRAMES).

HTTP-EQUIV tags

META tags with an HTTP-EQUIV attribute are equivalent to HTTP headers. Typically, they control the action of browsers, and may be used to refine the information provided by the actual headers. Tags using this form should have an equivalent effect when specified as an HTTP header, and in some servers may be translated to actual HTTP headers automatically or by a pre-processing tool.

HTTP headers are defined in RFC1945 (HTTP/1.0) and RFC2068 (HTTP/1.1). Note that RFC2068 states that multiple headers with the same name may be present only if the values may be concatenated.

HTTP headers may be generated by CGI scripts, and in Apache and CERN httpd by using a side file containing metadata. Other servers may have other mechanisms to generate headers. Note that certain server-generated headers may not be overridden (such as Date), and that others are only meaningful with a non-200 status code. Using an HTTP header is preferable to using META tags, since the header will be understood by cache agents and proxies in addition to browsers, and metadata (such as PICS data) may be associated with image files, sound files, etc.

However, new HTTP headers should not be created without checking for conflict with existing ones since it is possible to interfere with server and proxy operation.

Expires

Source:HTTP/1.1 (RFC2068)

The date and time after which the document should be considered expired. Controls cacheing in HTTP/1.0. In Netscape Navigator, a request for a document whose expires time has passed will generate a new network request (possibly with If-Modified-Since). An illegal Expires date, e.g. "0", is interpreted as "now". Setting Expires to 0 may thus be used to force a modification check at each visit.

Web robots may delete expired documents from a search engine, or schedule a revisit.

Dates must be given in RFC850 format, in GMT. E.g. (META tag):

<META HTTP-EQUIV="expires" CONTENT="Wed, 26 Feb 1997 08:21:57 GMT"> or (HTTP header):

Expires: Wed, 26 Feb 1997 08:21:57 GMT In HTTP 1.0, an invalid value (such as "0") may be used to mean "immediately".

See also Cache for discussion about cache control, page expiry, etc.

Pragma

Controls cacheing in HTTP/1.0. Value must be "no-cache". Issued by browsers during a Reload request, and in a document prevents Netscape Navigator cacheing a page locally.

Content-Type

Source:HTTP/1.0 (RFC1945)

The HTTP content type may be extended to give the character set. As an HTTP/1.0 header, this unfortunately breaks older browsers. As a META tag, it causes Netscape Navigator to load the appropriate charset before displaying the page. E.g.

<META HTTP-EQUIV="Content-type" CONTENT="text/html; charset=ISO-2022-JP">

 

Source:HTML 4.0 draft

Specifies the default scripting language in a document. See MIMETYPES for applicable values.

 

Source:HTML 4.0 draft

Specifies the default style sheet language for a document.

Content-Language

Source:HTTP/1.0,RFC1766

May be used to declare the natural language of the document. May be used by robots to categorize by language. The corresponding Accept-Language header (sent by a browser) causes a server to select an appropriate natural language document. E.g.

<META HTTP-EQUIV="Content-language" CONTENT="en-GB"> or (HTTP header)

Content-language: en-GB languages are specified as the pair (language-dialect); here, English-British

Refresh

Source:Netscape

Specifies a delay in seconds before the browser automatically reloads the document. Optionally, specifies an alternative URL to load. E.g.

<META HTTP-EQUIV="Refresh" CONTENT="3;URL=http://www.some.org/some.html">
 or (HTTP header)

Refresh: 3;URL=http://www.some.org/some.html In Netscape Navigator, has the same effect as clicking "Reload"; i.e. issues an HTTP GET with Pragma: no-cache (and If-Modified-Since header if a cached copy exists).

Window-target

Source:Jahn Rentmeister

Specifies the named window of the current page; can be used to stop a page appearing in a frame with many (not all) browsers. E.g.

<META HTTP-EQUIV="Window-target" CONTENT="_top">
 or (HTTP header)

Window-target: _top

Ext-cache

Source:Netscape

Defines the name of an alternate cache to Netscape Navigator. E.g.

<META HTTP-EQUIV="Ext-cache" 
CONTENT="name=/some/path/index.db; instructions=User Instructions">

Set-Cookie

Source:Netscape Navigator

Sets a "cookie" in Netscape Navigator. Values with an expiry date are considered "permanent" and will be saved to disk on exit. E.g.

<META HTTP-EQUIV="Set-Cookie" 
CONTENT="cookievalue=xxx;expires=Friday, 31-Dec-99 23:59:59 GMT; path=/">

PICS-Label

Source:PICS

Platform-Independant Content rating Scheme. Typically used to declare a document's rating in terms of adult content (sex, violence, etc.) although the scheme is very flexible and may be used for other purposes.

Cache-Control

Source:HTTP/1.1

Specifies the action of cache agents. Possible values:

  • Public - may be cached in public shared caches
  • Private - may only be cached in private cache
  • no-cache - may not be cached
  • no-store - may be cached but not archived

Note that browser action is undefined using these headers as META tags.

Vary

Source: HTTP/1.1

Specifies that alternates are available. E.g.

<META HTTP-EQUIV="Vary" CONTENT="Content-language"> or (HTTP header)

Vary: Content-language implies that if a header Accept-Language is sent an alternate form may be selected.

Lotus

The Lotus publishing tool generates Bulletin-Date and  Bulletin-Text attributes. Bulletin-Text contains a document description.

NAME attributes

META tags with a name attribute are used for other types which do not correspond to HTTP headers. Sometimes the distinction is blurred; some agents may interpret tags such as "keywords" declared as either "name" or as "http-equiv".

 

Robots

Source: Spidering

Controls Web robots on a per-page basis. E.g.

<META NAME="ROBOTS" CONTENT="NOINDEX,FOLLOW"> Robots may traverse this page but not index it.

Description

Source: Spidering,AltaVista,Infoseek.

A short, plain language description of the document. Used by search engines to describe your document. Particularly important if your document has very little text, is a frameset, or has extensive scripts at the top. E.g.

<META NAME="description" CONTENT="Citrus fruit wholesaler.">

Keywords

Source:AltaVista,Infoseek .

Keywords used by search engines to index your document in addition to words from the title and document body. Typically used for synonyms and alternates of title words. E.g.

<META NAME="keywords" CONTENT="oranges, lemons, limes">

Author

Source: Publishing tools, e.g. Netscape Gold

Typically the unqualified author's name.

Generator

Source: Publishing tools, e.g. Netscape Gold, FrontPage, etc.

Typically the name and version number of a publishing tool used to create the page. Could be used by tool vendors to assess market penetration.

Formatter

Source: Publishing tools - Microsoft FrontPage

Classification

Source: Netscape Gold

Undefined.

Copyright

Source: Publishing tools

Typically an unqualified copyright statement.

Rating

Source: mk-metas, Weburbia (safe for kids)

Simple content rating.

VW96.ObjectType

Source: mk-metas

Based on an early version of the Dublin Core report, using a defined schema of document types such as FAQ, HOWTO.

 

Defined by Queen's University of Belfast; a restricted set including e.g. "Contact Information", "Image".

Dublin Core

DC.TITLE, DC.CREATOR, DC.SUBJECT, DC.DESCRIPTION, DC.PUBLISHER, DC.CONTRIBUTORS  DC.DATE, DC.TYPE, DC.FORMAT, DC.IDENTIFIER, DC.SOURCE, DC.LANGUAGE, DC.RELATION, DC.COVERAGE, DC.RIGHTS

Dublin Core Elements. See the Reference Description

HTML 4.0

The HTML 4.0 Draft is now available.

HTdig

htdig-keywords, htdig-noindex

HTdig tags. See the HTdig META page.

 HTdig notification

htdig-email, htdig-notification-date, htdig-email-subject - see HTdig notification.

searchBC

searchBC is a regional search engine which uses a number of common tags such as Keywords. revisit is used as a hint for scheduling revisits.

Apple META tags

Author-Corporate, Author-Personal, Author-Personal, Publisher-Email, Ident ifier-URL, Identifier, Coverage, Bo okmark -

Kodak

EKBU, EKdocType, EKdocOwner, EKdocTech, EKreviewDate, EKArea - as used by Eastman Kodak.

IBM

ABSTRACT, CC, ALIAS, OWNER - as used by IBM.

Page-Enter, Page-Exit, Site-Enter, Site-Exit

Source: Microsoft DHTML

Defines special effects transition; e.g.

<meta http-equiv="Page-Enter"
content="revealTrans(Duration=3.0,Transition=2)"> See e.g. Transitions Between Pages

SHOE

Instance-Delegate, Instance-Key - see the SHOE Project at the University of Maryland (Simple HTML Ontology Extensions)

Microsoft Word

Microsoft Word 97 supports a number of HTML META attributes in the HTML export option. Content-Type is used to set the charset, Generator is set and various other tags may optionally be set.

SIC87

1987 US SIC (Standard Industry Codes), used in Vancouver Webpages Classifieds. See US SIC Codes

RDU

The Metadata Search Engine lists many tags, including the following:

  • contributor
  • custodian
  • custodian_contact
  • custodian_contact_position
  • east_bounding_coordinate
  • north_bounding_coordinate
  • relation
  • reply-to
  • south_bounding_coordinate
  • west_bounding_coordinate

Other Organisations

  • DMV MetaData for Mathematical Papers
  • Maple Square (ex. Sympatico)

Agent Markup Language

See the AML pages.

  • Agent markup Language Version

 

GILS

Government Information Locator Service - a US government initiative. See

  • Washington GILS metadata attribute set
  • GILS profile (version 2)

IMS

See the  IMS Project homepage. 

  • Dictionary

 

Fireball

The German search engine Fireball. See the metadata page and meta-tag generator. Supports Author, Publisher, Keywords, Description plus page-topic, page-type.

Miscellaneous

  • Version
  • Template
  • Operator
  • Creation
  • Host
  • Document
  • Subject
  • Build
  • Distribution - global,local, iu
  • Resource-type - document (for ALIWeb)
  • Location (geographic location; from Sympatico)

Deprecated:

  • Random Text (e.g., META NAME="Tom Jones")

Web Counts

Attributes in use counted by a Web robot here.
Also counted 3 July 97.
IAFA Template Statistics from the ROADS project

Other Resources

Thesauri

  • GETTY Art & Architecture Thesaurus
  • GETTY Artist Names Thesaurus
  • TGN - GETTY Thesaurus of Geographic Names
  • TGM I US Library of Congress Thesaurus for Graphic Materials I: Subject Terms
  • TGM II US Library of Congress Thesaurus for Graphic Materials II: Genre and Physical Characteristic Terms
  • LIV US Library of Congress Legislative Indexing Vocabulary
  • GLIN US Library of Congress Global Legal Information Network (GLIN) Thesaurus
  • ISSN (International Standard Serials Number)
  • LCSH (paper/CDROM)
  • LCSH, (telnet)

Other METAdata

Previous page...

Back to Top of Page

© 2002 Ashley Preston 

Computeach International Ltd

Christopher Ward London Limited

Christopher Ward London Limited