META Tag Dictionary
META tags have two possible attributes:
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 2012 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:
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, Identifier-URL, Ident ifier, 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 (Ruleweb)
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:
Other Organisations
Agent Markup Language
See the
AML
pages.
GILS
Government Information Locator Service - a US government
initiative. See
IMS
See the
IMS
Project
homepage.
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
Deprecated:
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
Other METAdata
- 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 2012 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, Identifier-URL, Ident ifier, 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 (Ruleweb)
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
- Resource Description
Framework
(RDF) - a W3C specification
- The
- META
Generator
(CGI script) - REL, REV tags
- Resource
Description
(Connolly) - Metadata
Architecture
(TimBL, Jan 97) - META
reference
by Galactus - HTML
3.2
- META Tagging for Search
Engines
at stars.com - draft-musella-html-metatag-01.txt,version
2
- HTML Writers Guild FAQ
- Jaggery the Rascal's
notes.
- metadata at ERIN
- report
from
the May 96 Indexing
Workshop
- draft-daviel-metadata-reg.txt (not.)
- Dublin Core
Generator
at UKOLN - Dublin Core Metadata
Template
at Nordic Metadata Project - Linking Metadata (draft-daviel-metadata-link-00.txt)
- ADAM Quick Guide to
Metadata
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
- Metadata Resources at IFLA
- Metadata standards
directories
by CESSE (Belgium) - Conferences in
1997
- Workshop on Metadata
Registries
(July 1997) - Metadata
Search Engine
- MetaWeb - the Australian metadata
project at DSTC - The
Metadata Repository Service
- Meta Content Framework uwing XML (Netscape)
- MCF Specification
- MCF Vocabulary
- MCF File Spec.
- NSDI MetaData
- SHOE
Project
- ROADS
Project
- PICS-SE (AID)
- WebDAV
proposal
- GILS (US Gov.t Information
Locator Service), see also v2
differences
