PageRank has been used to rank spaces or streets to predict how many people (pedestrians or vehicles) come to the individual spaces or streets. In lexical semantics it has been used to perform Word Sense Disambiguation, Semantic similarity, and also to automatically rank WordNet synsets according to how strongly they possess a given semantic property, such as positivity or negativity.
On the other hand, all of the results for the PageRank engine (aside from a single secondary listing) link to the homepage of major American universities. The results are much more logical and useful in nature. If you search for “university,” are you going to want the homepages for popular universities, or random subpages from a sprinkling of colleges all over the world?
7. Keyword research. Specific target keywords aren’t as important for SEO success as they used to be, now that Google search is fueled by semantic and contextual understanding, but you should still be able to identify both head keyword (short, high-volume keywords) and long-tail keyword (longer, conversational, low-volume keywords) targets to guide the direction of your campaign.
By relying so much on factors such as keyword density which were exclusively within a webmaster's control, early search engines suffered from abuse and ranking manipulation. To provide better results to their users, search engines had to adapt to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed with numerous keywords by unscrupulous webmasters. This meant moving away from heavy reliance on term density to a more holistic process for scoring semantic signals. Since the success and popularity of a search engine is determined by its ability to produce the most relevant results to any given search, poor quality or irrelevant search results could lead users to find other search sources. Search engines responded by developing more complex ranking algorithms, taking into account additional factors that were more difficult for webmasters to manipulate. In 2005, an annual conference, AIRWeb, Adversarial Information Retrieval on the Web was created to bring together practitioners and researchers concerned with search engine optimization and related topics.
Gaining Google's trust doesn't happen overnight. It takes time. Think about building up your relationship with anyone. The longer you know that person, the more likely that trust will solidify. So, the reasoning is, that if Google just met you, it's going to have a hard time trusting you. If you want Google to trust you, you have to get other people that Google already trusts, to vouch for you. This is also known as link-building.
9. Troubleshooting and adjustment. In your first few years as a search optimizer, you’ll almost certainly run into the same problems and challenges everyone else does; your rankings will plateau, you’ll find duplicate content on your site, and you’ll probably see significant ranking volatility. You’ll need to know how to diagnose and address these problems if you don’t want them to bring down the effectiveness of your campaign.