Content-Disposition

Source: RFC2183 - Specify application handler (Microsoft), e.g.
Content-Type: text/comma-separated-values  Content-Disposition: inline; filename=openinexcel.csv  

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".

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.

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">  
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.

Content-Script-Type

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.

Content-Style-Type

E.g.
<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css">  
Source: HTML 4.0

Specifies the default style sheet language for a document.

Default-Style

Source: HTML 4.0

Set the document's preferred style sheet, taken from an stylesheet specified elsewehere e.g. in a LINK element.

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).

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'>)

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.

See also the PICS HOWTO.

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.

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.

Altavista supports:

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.

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

Copyright

Source: Publishing tools

Typically an unqualified copyright statement.

Rating

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

Simple content rating.

HTML 4.0

The HTML 4.0 Specification.

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.

Apple META tags

Author-Corporate, Author-Personal, Author-Personal, Publisher-Email, Identifier-URL, Identifier, Coverage, Bookmark -

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)

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.

Geotags

Geographic Tagging for Resource Discovery.

Google

See Google Remove Content

MSSmartTags

UnSpam

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