Visibility on the Web is important for many people and commercial organisations as for many it has become one of the key issues for successful business. Most of the visibility is obtained through top rankings in search engine results. Simultaneously the end users have begun to rely more and more on search engines to locate the content they seek as finding information otherwise on the Web has become notoriously difficult. These issues have lead to an increased interest on search engine results as the top results gain more visitors than others. Due to importance of visibility, many companies and individuals try manipulate the search engine ranking algorithm for their benefit, so that their site would appear among the top results. This deteriorates the search engine functionality and has forced the search engine developers to develop new ranking algorithms and anti-spam filters. This race for top rankings has lead to a new digital arms race on the Web. This study investigates methods that are used by each of the two sides and also explores the adversarial relationship that has developed between them. The study is one of the most comprehensive papers that have been done on the topic.