Both algorithms are quite old in the search engine arena (2005), but are still in use, as is the initial PageRank algorithm (though much tweaked over time). You need to be aware of both in order to understand search engines better.
In this article we discuss Hilltop and TrustRank, the reasons behind those algorithms, and how to optimize better with each algorithm in mind. We also link to the official white papers that cover each algorithm and useful resources so you can learn and become more effective in SEO game.
Google Trust Rank
…we propose techniques to semi-automatically separate reputable, good pages from spam. We first select a small set of seed pages to be evaluated by an expert. Once we manually identify the reputable seed pages, we use the link structure of the web to discover other pages that are likely to be good….
To summarize how Trust Rank works, a page is first identified by a human as being of very high quality, or a "seed page." Pages that the "seed page" links to are classified as high quality pages as well. Pages that are linked from seed pages get high Trust Rank, and the further a page is from a seed page in the web’s link structure, the less Trust Rank is passed on to it.
Once seed pages are identified, it is easier to separate spam from quality pages. The logic behind Trust Rank is the following:
Quality pages do not link to spam (usually).
The trust score is reduced as it passes from page to page.
The most “powerful” trust score is from a seed page itself.
Examples of seed sites:
Ankhenaton, member of the Webmaster World makes an interesting point:
trustrank is the admittance that algorithms can’t make reliable choices about quality in a commercial real world scenario.
Factors such as the pages you link to are given weight.
Human evaluated authority sites are given more linking power.
TrustRank is another algorithm in the long battle for quality by 19,000+ Google employees. Low quality PR directory listings can still help, but, as many SEO professionals have preached for years, they’re dying and have less value each month. In order to stay afloat, we must figure out how to get links from “seed pages” and authoritative sites, which in a sense is a networking skill.
Aaron Wall of seobook.com has said for a long time that it’s better to view the Internet as a vast social network, and this is even truer today. Links show relationships between people, and the best links cannot be bought — just like relationships.
How Can We Use Trust Rank in Search Engine Optimization?
If you are in a competitive marketplace, it’s likely that Google uses Trust Rank to determine seed pages and filter out commercial spam. The trick SEOs face is to spot those “seed pages” or “seed sites” and get links from those pages.
As you analyze potential sites from which to get links, look for ones that might be “seed sites” or have “seed pages” within them. How editorial is the website? How authoritative is it? How useful is the information on it? How old is the domain?
The last question is important, because new commercial domains are not likely to be flagged as “seed sites,” while old domains that started commercial-free and developed some sort of business model have a greater chance of being a “seed sites” or having “seed pages” within.
If you think the site has “seed” potential, then it’s worth the effort to get links from that website. It may cost you money or time, but at worst you will earn a quality link.
Since TrustRank is quite old in the search engine world, it’s likely it was adjusted and improved over the years, both on Google’s vast test servers and on main indexes. There is no doubt that authority links are worth gold, and “seeds” are at the core of authority links.
…we propose a novel ranking scheme for broad queries that places the most authoritative pages on the query topic at the top of the ranking. Our algorithm operates on a special index of "expert documents." These are a subset of the pages on the WWW identified as directories of links to non-affiliated sources on specific topics. Results are ranked based on the match between the query and relevant descriptive text for hyperlinks on expert pages pointing to a given result page…
Hilltop is another “old” algorithm implemented by Google. Big G realized there was a problem with PageRank, since link authority could be passed from any page, to any page, regardless of topical relevance, making websites which got links from completely irrelevant sources rank high in search results.
The benefit of Hilltop over raw PageRank (Google) is that it is topic sensitive – and is thus generally harder to manipulate than buying some random high power off topic link would be. – seobook.com
Hilltop supposedly fixed this issue, and now a high PR link from a flower website to an automotive website does not count as it used to. There may be some value passed, but it is not as much as getting high PR link from an “authoritative” automotive site.
Hilltop is similar to Trust Rank, but more automated. It relies on “expert” documents and links from those documents, assuming:
X links to Y and Y links to Z, then X and Z are related.
The Hilltop paper also states that <titles> and <h-tags> are highly important, which is very true in everyday search engine optimization practice. Russ Jones in SEOmoz’s Search Engine Ranking Factors called the <title> tag:
the most powerful HTML tag you have at your disposal
Optimizing for Google Hilltop
Optimizing for Hilltop requires you to spot “expert documents” and essentially get links from those documents. There is nothing new here; it’s Link Building 101. Shoot for the most editorial links you can get from the most authoritative websites.
Spotting an authoritative website
The easiest way to spot an authoritative site is to look for a site in search results with an authoritative listing that includes “sitelinks.”
Site links (image example) are links below the first search result. Some websites have reached a high authority status and rank for generic terms with sitelinks. For the most part, sitelinks are shown for brand searches like “seo chat,” but once a site is shown with sitelinks for a generic term like “seo,” that website is a highly trusted authority on that topic.
Getting a link from there is worth gold.
Also look at the back link profile of the site you consider to be an “authority.” You may find the root hubs that link to the site in question are even more authoritative. Use Yahoo Site Explorer to explore backlinks, since Google dupes results for the “link:” command as anti-SEO measure.
Hilltop and TrustRank are both measures Google instituted against spam and overly aggressive search engine optimization techniques. Before both were implemented, search engine optimizers could get high PR links and dominate the top spots for competitive terms. With those algorithms in place, the game is a lot harder. Instead of hunting for PageRank alone, your link building strategy must focus on authority links first.
Mixing your link profile
Google is very good at link analysis. If you have only authority, expert and “seed” links, your link profile may look suspicious and alert algorithms that you’re doing SEO. In order to keep your link profile natural, get links from new and less trusted websites as well.
Networking with real people
It’s far easier to get authority links if you network with real people, know them in person and spend time with them. A link from the Wall Street Journal in an editorial article is worth much more than 10 links from generic directories with decent PR. If you’re a professional optimizing on your own, without outside help, then take the time to get to know people in your industry. Talk to journalists and bloggers, and make friends.
Large SEO companies often can only buy links and submit to directories. If you want to hire a company and expect to get many authoritative links, you will probably be disappointed. SEO copywriters get only several hours to research your topic… and how many years have you spent in your industry? You have the power to develop far more “authoritative” content that is interesting to experts in your field who have the golden keys to “expert pages” and “authoritative sites.” Hire an SEO company, but try unlocking the most precious links yourself.