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((((((((((((((((( WEBREFERENCE UPDATE NEWSLETTER ))))))))))))))))) May 17, 2001

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This week Scott Clark talks about getting back to basics--with META tags.

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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 2. FEATURED ARTICLE: Back to Basics: META Tags

With all the new HTML tags that are coming out, itÂ’s easy to overlook some of the greatest tools in our arsenal of HTML tricks. There are still a few HTML goodies lying around thatÂ’ll help you keep your pages more up to date, make them easier to find, and even stop them from becoming framed. WhatÂ’s more, some of these tags have been with us since the first Web browsers were released.

META tags can be very useful for Web developers. They can be used to identify the creator of the page, what HTML specs the page follows, the keywords and description of the page, and the refresh parameter (which can be used to cause the page to reload itself, or to load another page). And these are just a few of the common uses!

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 youÂ’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.

Back to META tags. Just 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. Certain Web servers may translate META HTTP-EQUIV tags into actual HTTP headers automatically so that the userÂ’s Web browser would simply see them as normal headers. Some Web servers, such as Apache and CERN httpd, use a separate text file which contains meta-data. A few Web server-generated headers, such as "Date," may not be overwritten by META tags, but most will work just fine with a standard Web server.

NAME META tags with a NAME attribute are used for META types which do not correspond to normal HTTP headers. This is still a matter of disagreement among developers, as some search engine agents (worms and robots) interpret tags which contain the keyword attribute whether they are declared as "name" or "http-equiv," adding fuel to the fires of confusion.

Using META Tags On to more important issues, like how to actually implement META tags in your Web pages. If youÂ’ve ever had readers tell you that theyÂ’re seeing an old version of your page when you know that youÂ’ve updated it, you may want to make sure that their browser isnÂ’t caching the Web pages. Using META tags, you can tell the browser not to cache files, and/or when to request a newer version of the page. In this article, weÂ’ll cover some of the META tags, their uses, and how to implement them.

Expires This tells the browser the date and time when the document will be considered "expired." If a user is using Netscape Navigator, a request for a document whose time has "expired" will initiate a new network request for the document. 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 Netscape Navigator 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. Many users have reported that Microsoft’s Internet Explorer refuses the META tag instructions, and caches the files anyway. So far, nobody has been able to supply a fix to this "bug." As of the release of MSIE 4.01, this problem still existed.

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. <META HTTP-EQUIV="Refresh" CONTENT="0;URL=http://www.newurl.com">

Be sure to remember to place quotation marks around the entire CONTENT attributeÂ’s value, or the page will not reload at all.

Set-Cookie This is one method of setting a "cookie" in the userÂ’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 Although you may not have heard of PICS-Label (PICS stands for Platform for Internet Content Selection), you probably will soon. 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 W3CÂ’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 Chances are that if you manually code your Web pages, youÂ’re aware of 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. CouldnÂ’t be simpler, right? You use the keywords attribute to tell the search engines which keywords to use, like this: <META NAME ="keywords" CONTENT="life, universe, mankind, plants, relationships, the meaning of life, science">

By the way, donÂ’t think you can spike the keywords by using the same word repeated over and over, as most search engines have refined their spiders to ignore such spam. 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. To do that, just use the regular comment tags, like this: <!-- This page is about the meaning of life, the universe, mankind and plants. -->

ROBOTs in the mist On the other hand, there are probably some of you who do not wish your pages to be indexed by the spiders at all. Worse yet, you may not have access to the robots.txt file. The robots META attribute was designed with this problem in mind. <META NAME="robots" CONTENT="all | none | index | noindex | follow | nofollow">

The default for the robot attribute is "all". This would allow all of the files to be indexed. "None" would tell the spider not to index any files, and not to follow the hyperlinks on the page to other pages. "Index" indicates that this page may be indexed by the spider, while "follow" would mean that the spider is free to follow the links from this page to other pages. The inverse is also true, thus this META tag: <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. "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 W3CÂ’s robot paper.

Placement of META tags META tags should always be placed in the head of the HTML document between the actual

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.

Obscure META Tags WeÂ’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?

If youÂ’re a normal person (IÂ’m not, and I donÂ’t know any, but I heard they do exist), then youÂ’re wondering just what, exactly, is Dublin Core? No, itÂ’s not an Irish porno movie, but rather, itÂ’s a simple resource description record that has come to be known as the Dublin Core Metadata element set, or rather, Dublin Core.

Thanks to a considerate reader, we now know how it got its name. 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.

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 WebpagesÂ’ 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 couldnÂ’t hurt to use both.

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, youÂ’ll notice that they automatically insert certain META tags, such as Generator, Content-Type, etc. into the Web page source. Other META tags are organization or search engine specific. The RDU Metadata search engine uses many such tags, including: contributor, custodian, east_bounding_coordinate, north_bounding_coordinate and others. Other obscurities are government META tags, useful only if you are within a government intranet or system.

But then... Statistics show that only about 21% of Web pages use keyword and description META tags. If you use them and your competitor doesnÂ’t, thatÂ’s one in your favor. If your competitor is using them and you arenÂ’t, you may now consider yourself armed with the knowledge. META tags are something that visitors to your Web site are usually not aware of, but ironically, a lot of times it was those same META tags which enabled them to find you in the first place. So for goodnessÂ’ sake, donÂ’t tell anyone about this... letÂ’s just keep this our own little secret (just kidding...make sure to send this URL to everyone you know!).

The Law Before we leave the topic of META tags, keep in mind that there are several legal issues that surround the use of these tags on your Web site. Danny Sullivan, editor of SearchEngineWatch, has put together a page detailing the lawsuits brought on revolving around META tags. At the present time there have already been at least five such suits, mainly focused on sites that utilized someone else's keywords within their META tags. The largest of these suits brought a settlement of $3 million dollars. Bottom line: use your own keywords, and definitely not words that someone else has a copyright on.

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 youÂ’d like some assistance creating the META tags, check out Andrew DavielÂ’s form-based META tag generator.

---------------------- Scott Clark is the Executive Editor of internet.com's Web Developer Channel. Previously, he was Managing Editor of WDVL.com and JavaBoutique.com, as well as Technical Editor for Web Developer magazine and later, WebDeveloper.com. He has been part of the Dr. Website team for the last 5 years, and continues to love discovering and using new internet technologies.

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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 3. NET NEWS: Cheese the Friendly Worm On the Loose Password Glitch Exposes DSL Subscribers Intruder Alert, MS IIS Found Vulnerable to Remote Hacking

>Cheese the Friendly Worm On the Loose

According to the Computer Emergency Response Team at Carnegie Mellon, the Cheese worm exploits the same back door Lion used, applies a patch to eliminate the back doors left by Lion, then runs scans from the host it's just visited to find other infected machines with port 10008 open, and spreads to them, applying its patch as it goes. http://linuxtoday.com/news_story.php3?ltsn=2001-05-17-002-20-SC

>Password Glitch Exposes DSL Subscribers

Cayman Systems says SBC and other customers don't want router password protection enabled. As a result, hundreds of DSL subscribers are wide open to attack. http://www.computerworld.com/cwi/story/0,1199,NAV47_STO60203,00.html

>Intruder Alert, MS IIS Found Vulnerable to Remote Hacking

A serious vulnerability in Microsoft IIS may allow remote intruders to execute commands on an IIS Web server. http://www.infoworld.com/articles/ca/xml/01/05/07/010507cajob.xml

That's it for this week, see you next time.

Scott Clark Executive Editor, Web Developer Channel update@webreference.com

Dan Ragle Assistant Editor, WebReference.com dragle@internet.com

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