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If so, often this is done so that a search engine spider will follow the links and spider the target URL pages as well, or it is done to add relevancy to the page subject matter by directing the spider to relevant sites. All the while, there is no trace of the links on the page that regular visitors see.
It is considered a spamming technique by most engines but it is very gray, and not usually penalized unless you overdo it and someone complains. With most engines now counting inbound links and the content from those links as a means of determining relevance this technique has diminishing value.
It is still widely used and will help on some engines if done correctly. But with themes and link popularity becoming more prevalent it is probably best to cultivate real links inbound and outbound, with the inbound links from relevant sites being the more important.
If you want to do something like that for link text purposes, just link it to your index page or other big page on your site.