This page assumes you've already read the Search Engines And Capitalization page in the main site. It explains that most people search in lower case and advises you not to worry much about covering all the possible capitalization forms. But people do worry, so this page provides some tips on covering the bases without getting into trouble.
There are two basic strategies you can follow to help increase the odds your page will turn up when someone specifies case in a case-sensitive search engine. One is conservative, the other is for those absolutely paranoid about missing out on traffic.
In both cases, let's pretend that you run StarPages, a science fiction book shop. You hope to be found for "science fiction books," but you want to ensure you get people who also enter "Science Fiction Books" or "SCIENCE FICTION BOOKS."
In the conservative plan, you don't want any risk against missing out on that important lower-case traffic. So you play it safe and use only lower-case terms in your meta tags. You cover the upper/lower variation (also called Title Case) in your page title and in your actual page copy.
StarPages: Science Fiction Books and Magazines
science fiction books, magazines, memorabilia
StarPages is your resource for science fiction books and magazines on the web. We have over 3,000 titles.
HTML Body Copy:
At StarPages, we want to help you find the science fiction books you are looking for...
In the example above, Title Case is used in the title field. It could have been used again in the keywords field, instead of lower case, but the mixture in two different areas may help ensure the page does well.
A more comprehensive approach would be to include the use of an all caps variation somewhere on the page. The ideal place for this is in the meta keywords field, since this is not visible to the user. They aren't likely to appreciate seeing SCIENCE FICTION BOOKS in the visible fields, such as the title or in the body copy.
The downside to this is that you may not wish to have both a lower and uppercase variation both in the keywords tags, in order to avoid problems with spam detectors. That means that you'd go without a lowercase variation there.
Possibly, that could lower your relevancy for that term. That's heavy emphasis on the possibly, since there's no research that shows this is true. But if you are concerned, then play it safe and go with the lowercase version.
Don't forget, you have other pages within your web site. Perhaps one of these is an appropriate place for an all caps version. That's also helpful because not all search engines support the meta keywords tag.
In the end, the main issue is not to be too concerned. Using case variations is not going to bring you huge amounts of traffic, nor cost you huge amounts should you fail to anticipate every variation possible.
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