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).
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".
Note: While the Expires HTML
META tag appears to work properly
with Netscape Navigator, other
browsers may ignore it, and it is
ignored by Web proxies. Use of the
equivalent HTTP header, as supported
by e.g. Apache, is more reliable.
See also
CacheNow for discussion
about cache control, page expiry,
etc.
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.
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">
It is
now recommended to always use this
tag, even with the
previously-default charset
ISO-8859-1. Failure to do so may
cause display problems where, for
instance, the document uses UTF-8
punctuation characters but is
displayed in ISO or ASCII charsets.
E.g.
<META HTTP-EQUIV="Content-Script-Type" CONTENT="text/javascript">
Source: HTML 4.0
Specifies the default scripting
language in a document. See
MIMETYPES for applicable values.
E.g.
<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css">
Source: HTML 4.0
Specifies the default style sheet
language for a document.
Source: HTML 4.0
Set the document's preferred style
sheet, taken from an stylesheet
specified elsewehere e.g. in a LINK
element.
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
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).
Note: If a script is executed which
reloads the current document, the
action of the Refresh tag may be
undefined. (e.g. <body onLoad= "document.location='otherdoc.doc'>)
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
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">
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=/">
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.
See also the
PICS HOWTO.
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.
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.
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".
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.
Altavista supports:
-
NOINDEX prevents anything on the
page from being indexed.
-
NOFOLLOW prevents the crawler
from following the links on the
page and indexing the linked
pages.
-
NOIMAGEINDEX prevents the images
on the page from being indexed
but the text on the page can
still be indexed.
-
NOIMAGECLICK prevents the use of
links directly to the images,
instead there will only be a
link to the page.
Google supports a NOARCHIVE
extension to this scheme to request
the Google search engine from
caching pages; see the
Google FAQ
See also the
/robots.txtexclusion
method.
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.">
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">
Source:
Publishing
tools, e.g.
Netscape Gold
Typically the unqualified author's
name.
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.
Source: Publishing tools -
Microsoft FrontPage
Source:
Netscape Gold
Undefined.
Source: Publishing tools
Typically an unqualified copyright
statement.
Source:
mk-metas,
Weburbia
(safe for kids)
Simple content rating.
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".
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
The
HTML 4.0 Specification
is now available.
htdig-keywords,
htdig-noindex
HTdig tags. See the
HTdig META page.
DC-CHEM
DC-CHEM. Chemical Metadata extensions
HTdig notification
htdig-email,
htdig-notification-date,
htdig-email-subject
- see
HTdig notification.
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.
Author-Corporate,
Author-Personal,
Author-Personal,
Publisher-Email,
Identifier-URL,
Identifier,
Coverage,
Bookmark -
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
(Filters & Transitions)
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)
Instance-Delegate,
Instance-Key
- see the
SHOE Project
at the University of Maryland
(Simple HTML Ontology Extensions)
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.
1987 US SIC
(Standard Industry Codes), used in
Vancouver Webpages Classifieds.
See
US
SIC Codes
The RDU Metadata Search Engine (original URL dead) listed many tags, including
the following:
Other Organisations
Agent Markup Language
See the
AML pages.
See
GeoCities categorize.
Government Information Locator
Service - a US government
initiative. See
IMS
See the
IMS Project homepage.
The German search engine
Fireball. See the
metadata page and
meta-tag generator.
Supports Author, Publisher,
Keywords, Description plus
page-topic, page-type.
Geographic Tagging for Resource
Discovery.
- googlebot: noarchive - do
not allow google to display
cached content
- googlebot: nosnippet - do
not allow google to display
excerpt or cached content
- googlebot: noindex - similar
to the robots meta
element
- googlebot: nofollow
See
Google Remove Content
- MSSmartTagsPreventParsing:
TRUE - prevent Microsoft Smart
Tags being applied to a page
See
glassdog.com/smarttags,
office.microsoft.com.
However, it looks at the moment as
if SmartTags have been abandoned.
An initative of unspam.com to forbid
compliant robots from harvesting
email addresses. Usage:
<meta name="no-email-collection" value="[link to your terms]" />
Replace the [link to your terms]
with a link to your terms of use
page. Alternatively you may include
a link to
www.unspam.com/noemailcollection
See
how_to_avoid_spambots
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
Other METAdata
Conferences in 1997
Workshop on Metadata Registries
(July 1997)
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