SEO Science: Search Engine Optimisation is a science. However Search Engines (SEs) deliver their top 10 pages, the delivery rational is based on gathered data (crawling), analysis (indexing) and keyword search relevance (the SE algorithm). Modern established SE algorithms are far more refined and sophisticated than their crude and simple predecessors developed in the early 1990s. In the early days of SEs, results were delivered purely based on keyword relevance within the HTML code of delivered pages. This is not the case anymore, but remains a very important part of SEO.