DES 3006 - Web Design II

Week Eleven | Part Two: Meta Tags (cont.)

4. The Robots Tag

This robots tag lets you specify that a particular page should NOT be indexed by a search engine. To keep site crawlers out, simply add this text between your head tags on each page you don't want indexed:

<META NAME="ROBOTS" CONTENT="index,nofollow">

The robots tag allows HTML authors to indicate to visiting robots if a document may be indexed, or used to harvest more links. No server administrator action is required. So, in my example, I specified that I only wanted my index page crawled, and not to follow the links on that page into my site. To have your entire site or area crawled, use:

<META NAME="ROBOTS" CONTENT="index,follow">

To prevent both index and site crawlers:

<META NAME="ROBOTS" CONTENT="noindex,nofollow">

5. No Cache and Page Expiry

<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="EXPIRES" CONTENT="31 Dec 2000 00:00:01 PST">

These tags are sometimes used in an attempt to reduce caching by the browser and by network caches, so the user always gets to see the most current version of the page, not one that has been stored by and recovered from some intermediate level in the Internet system.

The trick is to make the page expire immediately ("0" is an illegal value interpreted as meaning Now) or at some date in the past. This combination of tags certainly does reduce caching, but doesn't eradicate all of it. Many proxy caches choose to ignore these tags and go ahead with their caching anyway. Also, search engines may decide that since your page is out of date, they'd better remove it from their indexes.

6. The Rating Tag

<META NAME="RATING" CONTENT="General">

Meta tags can be used with ratings services to identify the sex and violence level of your content.

Site rating is hardly a magic cure. The rating meta tags only have an effect in certain situations, with certain browsers, and with certain users. If your site contains potentially controversial material, incorporating a ratings screening might offer you some degree of protection against critics.

A more comprehensive solution would be to use the Platform for Internet Content Selection, or PICS^TM, criteria.

The PICS^TM specification enables metadata to be associated with Internet content. It was originally designed to help parents and teachers control what children access on the Internet, but it also includes code signing and privacy. Several Internet rating services and filtering software use the PICS platform.

Refreshing or Redirecting your Visitors

The Refresh Tag goes within the <head> of your HTML document. When used to refresh the current page, the syntax looks like this:

<meta http-equiv="refresh" content="600">

This attribute tells the browser this meta tag is sending an HTTP command rather than a standard meta tag. Refresh is an actual HTTP header used by the Web server. It tells the server that the page is going to be reloaded or sent somewhere else.

content="600"

This is the amount of time, in seconds, until the browser should reload the current page.

Some of the more common uses of the reload version of the refresh tag is to reload a page that has dynamic content on it.

Redirecting to a New Page

While the reload option is useful, it is usually not what people want. To redirect to a new page, the syntax is nearly the same:

<meta http-equiv="refresh" content="2;url=http://webdesign.about.com">

The only difference is in the content attribute:

content="2;url=http://webdesign.about.com"

The number is the time, in seconds, until the page should be redirected. Then, separated by a semi-colon (;) is the URL (technically, the URI) that should be loaded.

Meta refresh tags have some drawbacks:

If the redirect happens quickly (less than 2-3 seconds), readers with older browsers can't hit the "Back" button. This is a usability problem.
If the redirect happens quickly and goes to a non-existent page, your readers won't be able to hit the "Back" button. This is a usability problem that will cause people to completely leave your site.
Refreshing the current page can confuse people. If they didn't request the reload, some people can get concerned about security.

Go to Week Eleven - Part III