Types | Using | Keyword | Robots | Uncommon | Program | Resources
META tags are an underutilized resource for Web developers. They can be identify the creator of the page, what HTML should be used by the browser to interpret the page, assist search engines in categorizing the site by keywords and description of the page, and much more.
First, there are two types of META tags: HTTP-EQUIV and META tags with a NAME attribute.
HTTP-EQUIV
META HTTP-EQUIV tags are the equivalent of HTTP headers. To understand what headers are, you need to know a little about what actually goes on when you use your Web browser to request a document from a Web server. When you click on a link for a page, the Web server receives your browser's request via HTTP. Once the Web server has made sure that the page you've requested is indeed there, it generates an HTTP response. The initial data in that response is called the "HTTP header block." The header tells the Web browser information which may be useful for displaying this particular document
Like normal headers, META HTTP-EQUIV tags usually control or direct the actions of Web browsers, and are used to further refine the information which is provided by the actual headers. HTTP-EQUIV tags are designed to affect the Web browser in the same manner as normal headers. There are variations on how META HTTP-EQUIV tags are handled between the different web servers available but most will work as if they were part of the actual header.
NAME
META tags with a NAME attribute are used for META types which do not correspond to normal HTTP headers. Some search engine agents (worms and robots) interpret tags which contain the keyword attribute whether they are declared as "name" or "http-equiv" .
Using META Tags
Placement of META tags
META tags should always be placed in the head of the HTML document between the actual <HEAD> tags, before the BODY tag. This is very important with framed pages, as a lot of developers tend to forget to include them on individual framed pages. Remember, if you only use META tags on the frameset pages, you'll be missing a large number of potential hits.
Older browsers may not correctly interpret meta tags, particularly the Expires and the NOCACHE attributes. Internet Explorer 5+ and Netscape Navigator 4+ should properly interpret these tags.
Expires
If you've ever had readers tell you that they're seeing an old version of your page when you know that you've updated it, you may want to make sure that their browser isn't caching the Web pages. This tells the browser the date and time when the document will be considered "expired." An illegal Expires date such as "0" is interpreted by the browser as "immediately." Dates must be in the RFC850 format, (GMT format):
<META HTTP-EQUIV="expires" CONTENT="Wed, 26 Feb 1997 08:21:57 GMT">
Pragma
This is another way to control browser caching. To use this tag, the value must be "no-cache". When this is included in a document, it prevents the browser from caching a page locally.
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
These two tags can be used as together as shown to keep your content current-but beware earlier versions of Internet Explorer (at least as late as 4.01) will ignore this tag.
Refresh
This tag specifies the time in seconds before the Web browser reloads the document automatically. Alternatively, it can specify a different URL for the browser to load. This is very handy when you have moved a page from one location to another but the original url is still appearing in search engines.
<META HTTP-EQUIV="Refresh" CONTENT="10;URL=http://wiserways.com/web-tech">
Tells the browser to load http://wiserways.com/web-tech 10 seconds after the current document has finished loading. Not all browsers support this, so you should provide an alternate means of moving to the new page such as a statement that the page has moved and the new url.. Some search engines penalize pages that use a Refresh of a few seconds or less. Be sure to remember to place quotation marks around the entire CONTENT attribute's value, or the page will not reload at all.
Set-Cookie
This is one method of setting a "cookie" in the user's Web browser. If you use an expiration date, the cookie is considered permanent and will be saved to disk (until it expires), otherwise it will be considered valid only for the current session and will be erased upon closing the Web browser.
<META HTTP-EQUIV="Set-Cookie" CONTENT="cookievalue=xxx;expires=Wednesday, 21-Oct-98 16:14:21 GMT; path=/">
Window-target
This one specifies the "named window" of the current page, and can be used to prevent a page from appearing inside another framed page. Usually this means that the Web browser will force the page to go the top frameset.
<META HTTP-EQUIV="Window-target" CONTENT="_top">
PICS-Label
You may not have heard of PICS-Label (PICS stands for Platform for Internet Content Selection), at the same time that the Communications Decency Act was struck down, the World Wide Web Consortium (W3C) was working to develop a standard for labeling online content (see www.w3.org/PICS/ ).
This standard became the Platform for Internet Content Selection (PICS). The W3C's standard left the actual creation of labels to the "labeling services." Anything which has a URL can be labeled, and labels can be assigned in two ways. First, a third party labeling service may rate the site, and the labels are stored at the actual labeling bureau which resides on the Web server of the labeling service.
The second method involves the developer or Web site host contacting a rating service, filling out the proper forms, and using the HTML META tag information that the service provides on their pages. One such free service is the PICS-Label generator that Vancouver-Webpages provides. It is based on the Vancouver Webpages Canadian PICS ratings, version 1.0, and can be used as a guideline for creating your own PICS-Label META tag.
Although PICS-Label was designed as a ratings label, it also has other uses, including code signing, privacy, and intellectual property rights management. PICS uses what is called generic and specific labels. Generic labels apply to each document whose URL begins with a specific string of characters, while specific labels apply only to a given file. A typical PICS-Label for an entire site would look like this:
<META http-equiv="PICS-Label" content='(PICS-1.1 "http://vancouver-webpages.com/VWP1.0/" l gen true comment "VWP1.0" by "scott@hisdomain.com" on "1997.10.28T12:34-0800" for "http://www.hisdomain.com/" r (P 2 S 0 SF -2 V 0 Tol -2 Com 0 Env -2 MC -3 Gam -1 Can 0 Edu -1 ))'>
Keyword and Description attributes
Now we are getting to the most commonly used meta tags, f the "keyword" and "description" attributes. These allow the search engines to easily index your page using the keywords you specifically tell it, along with a description of the site that you yourself get to write. Keywords would look like this:
<META NAME ="keywords" CONTENT="life, universe, mankind, plants, relationships, the meaning of life, science">
While writing your keywords may appear to be a simple task, it really has become an art form to get the best placement for your site by carefully crafting your keywords. We'll save that topic for another day. By the way, don't think you can spike the keywords by using the same word repeated over and over, most search engines consider that to be 'spam' and it can result in having your url permanently banned from being listed at all by that search engine.
Using the META description attribute, you add your own description for your page:
<META NAME="description" CONTENT="This page is about the meaning of life, the universe, mankind and plants.">
Make sure that you use several of your keywords in your description. While you are at it, you may want to include the same description enclosed in comment tags, just for the spiders that do not look at META tags.
ROBOTs
This tag will give instructions to the spiders that index the web and is very useful when you do no have access to the robots.txt file. Here is where you can instruct the spiders and worms how you would like each page treated. The attributes are self explainatory.
<META NAME="robots" CONTENT="all | none | index | noindex | follow | nofollow">
The default for the robot attribute is 'all'.
<META NAME="robots" CONTENT=" noindex">
Would tell the spider not to index this page, but would allow it to follow subsidiary links and index those pages while adding "nofollow" would allow the page itself to be indexed, but the links could not be followed. As you can see, the robots attribute can be very useful for Web developers. For more information about the robot attribute, visit the W3C's robot paper and Robots Exclusion Protocol
Uncommon META Tags
We've covered most of the popular and useful META tags, but what about the obscure ones that you hardly see, such as Dublin Core or rating?
What is Dublin Core? It's a simple resource description record that has come to be known as the Dublin Core Metadata element set, or rather, Dublin Core.
Dublin Core is the core set of metadata elements which were identified by a working group (comprised of experts drawn from the library and Internet communities) which met in Dublin, Ohio, not the better known city in Ireland..
Dublin Core was designed with several issues in mind, namely to:
- enable search engines to filter by standard fields, i.e. date and author
- Browsers could have the ability to display metadata fields in a separate window
- enhance cross-collection, repurposing and integrating of content
- enhance site management, as old pages may be located more easily, etc.
If you want to see what an actual Dublin Core META tag looks like, you can use Vancouver Webpages' Dublin Core META tag generator.
Rating is basically the same thing as PICS-Label, and can be used for the same purpose, but PICS-Label is recommended over rating, as it is currently recognized by more software than rating, although it couldn't hurt to use both.
Program Specific Meta tags
Many of the obscure META tags are produced by HTML authoring software. Microsoft Word supports a number of META attributes in its HTML export option, and if you create a document with Internet Assistant, FrontPage, etc, you'll notice that they automatically insert certain META tags, such as Generator, Content-Type, etc. into the Web page source.
Summary
Statistics show that only about 21% of Web pages use keyword and description META tags. If you use them and your competitor doesn't, that's one in your favor. If your competitor is using them and you aren't, you should seriously consider adding them. While META tags are something that most visitors to your Web site are usually not aware of a lot of times it was those same META tags which allowed them to find you in the first place. Just remember to review the policies of all of the search engines you intend to submit your site to for their policies and advice on crafting your keywords and site descriptions. Many such as Yahoo give detailed information on what they look for in meta tags.
Also, don't just copy the meta tags of the highest ranking site in you found using keywords that apply to your site. There have been several lawsuits over using someone else's keywords in your meta tags. For more information you may want to check SearchEngineWatch
Additional Resources:
For additional META information, be sure to check out the WebDeveloper.com META Tag Resource Page, as well as Galactus' META info page, and Vancouver's own META tag page. If you'd like some assistance creating the META tags, check out Andrew Daviel's form-based META tag generator.
META Tag Builder (online) http://vancouver-webpages.com/META/mk-metas.html
Meta Tag Analyzer (online) http://www.scrubtheweb.com/abs/meta-check.html
A Standard for Robot Exclusion http://www.scrubtheweb.com/abs/meta-check.html
What to do if you don't want to have robots or spiders index all or part of your site.
WDG Web Design Group Meta Tag http://www.htmlhelp.com/reference/html40/head/meta.html
Effectively using Meta Tags http://www.submitcorner.com/Guide/Improve/effectiveuse.shtml
Meta Tag generator http://www.submitcorner.com/Tools/Robots/