Spiders are sent out by search engines to evaluate sites for positioning within the search engine. These spiders are very impressed by high-quality links. They follow links and evaluate them based on their own ranking and relevancy to the site. It’s important that your incoming links be pertinent to the subject matter and come from well-respected sites. The quantity of links isn’t as important as the quality in this case. In fact it’s better to have 10 high-quality incoming links than 100 so-so incoming links from sites that have nothing to do with your own.