Search engine spam is one of the most difficult problems that search engine crawlers encounter. And it can be a real problem for web-site owners, too, because those who use search engine spam in an attempt to improve their site rankings make it even more difficult for legitimate web sites to achieve good rankings.

So, what exactly is search engine spam? Yahoo! defines it like this: Pages created deliberately to trick the search engine into offering inappropriate, redundant, or poor-quality search results.

Other search engines have a similar definition for search engine spam. Ultimately, what your concern with search engine spam should be is to avoid it at all costs. There’s a fine line between optimizing your web site and creating search engine spam. And you can cross that line unexpectedly. The problem is that search engines will penalize your site if they perceive any element of the site as being search engine spam. And in some cases, that penalty can be delisting your site from search rankings entirely.

There are more than a dozen types of search engine spam. Some types, like content scraping, we’ve already covered. But many more exist and in order to avoid them, you should know what they are.