For search engine optimization, it is important, that the website has a high topic relevance to the searched keywords. If this criterion is met, it is rewarded with a good ranking by the search engine. Topic relevance can be reached by the fact, that there is a substantive and/or formal similarity between the keywords and the website address. Even the headline of the document and the keyword density is included in the assessment of subject with relevance. The keywords should occur in the title, in the heading section and the entire site. However, it should not exaggerate. The search engine optimizer is aiming to make as many topic relevant links to the website as possible, because this approach is an increase in popularity, and thus a better positioning in the search engine results lists. A topic related link uses the keywords and the content of the site and promises depth information on this area.