Generally search engines prefer not to index . The one exception to this is that if you are a hosting company it might make sense to offer free hosting or a free mirror site to a popular software site to build significant link equity.
Please note that it is more important that copy reads well to humans than any boost you may think you will get by tweaking it for bots. If every occurrence of a keyword on a page is in emphasis that will make the page hard to read, convert poorly, and may look weird to search engines and users alike.
Search engines may analyze end user behavior to help refine and improve their rankings. Sites which get a high and have a high proportion of from may get a ranking boost in algorithms like Panda.
If you are buying pay per click ads it is important to send visitors to the most appropriate and targeted page associated with the keyword they searched for. If you are doing link building it is important to point links at your most appropriate page when possible such that
Some people believe in , but linking out to other related resources is a good way to help search engines understand what your site is about. If you link out to lots of low quality sites or primarily rely on low quality reciprocal links some search engines may not rank your site very well. Search engines are more likely to trust (both to and from your site).
Some search marketers lacking in creativity tend to describe services sold by others as being unethical while their own services are ethical. Any particular technique is generally not typically associated with ethics, but is either effective or ineffective.
For example, if a site publishes significant it may get a reduced crawl priority and get filtered out of the search results. Some search engines also have filters based on link quality, link growth rate, and . Some pages are also for .
Many paid links, such as those from quality , still count as signs of votes as long as they are also associated with editorial quality standards. If they are from sites without editorial control, like , they are not likely to help you rank well. Using an algorithm similar to , some search engines may place more trust on well known sites with strong editorial guidelines.
Many SEOs talk up fresh content, but fresh content does not generally mean re-editing old content. It more often refers to creating new content. The primary advantages to fresh content are:
In the past search engines were less aggressive at indexing dynamic content than they currently are. While they have greatly improved their ability to index dynamic content it is still preferable to use to help make dynamic content look in nature.
Fuzzy search technology is similar to technology, with the exception that fuzzy search corrects the misspellings at the users end and stemming searches for other versions of the same core word within the index.
Some search queries might require significant time for a user to complete their information goals while other queries might be things which are quickly answered by a landing page, thus dwell time in isolation may not be a great relevancy signal. However search engines can also look at other like , , relative & if users clicking on a particular listing have a high (by subsequently clicking on yet another different search result) to get an idea of a user's satisfaction with a particular webiste & fold these metrics into an algorithm like .
Google Base may also help Google better understand what types of information are commercial in nature, and how they should structure different vertical search products.
Search engines do not want to index multiple versions of similar content. For example, printer friendly pages may be search engine unfriendly duplicates. Also, many automated content generation techniques rely on recycling content, so some search engines are somewhat strict in filtering out content they deem to be similar or nearly duplicate in nature.