8: Ranking Algorithms Flashcards
What is SEO ?
Search Engine Optimisation
It improves the visibility of a website in search engines via unpaid (‘organic’) search.
Most internet traffic is referred to by search engines, and 90% don’t look past first 30% of results.
Advantages of SEO?
- People trust more links on search engine result pages than ad links
- Cheaper than adverts as improved visibility works in long-term
What is SERP?
Search Engine Result Pages
Disadvantages of SEO?
- Harder: requires good HTML design
- Competitive keywords
- Improvements not immediate
- Unable to target specific demographic groups (ala FB)
How does a search engine work ?
1) Spiders crawl the internet
2) Webpages are index in a huge DB
3) When a user searches for something, the engine finds the relevant webpages in their database.
4) The results are ranked according to an algorithm.
5) Users are only shown the top ranked results.
What is the realistic and non-realistic approach to do SEO?
Nonrealistic: study the same exact ranking algorithm used by an engine, adjust webpages accordingly.
Ranking algorithms are secret to detect and deter cheating, and also change all the time.
Realistic: study the big picture, improve visibility according to common ranking factors.
Ranking factors ?
- Keywords in URL, title, domain, body
- Links are stable, descriptive, valid, well-organised (tree)
- No typos, HTML mistakes, or taboo words
- Link popularity (PageRank)
How does PageRank roughly work ?
It works by counting the number and quality of links to a page to determine a rough estimate of how important the website it.
The more important pages are more likely to receive more links from other pages.
What is the PageRank of a web-page?
It is the probability that a web surfer arrives at the page by randomly clicking on links.
What is the PageRank formula ?
PR(x) = 0.15 + 0.85* SUM {from i=1 to n} (PR(y_i)/k_i)
Where:
- x is a specific web-page
- y_i are the sites with links to x
- k is the number of outbound links of the page y_i
- n is the total number of webpages
What is TrustRank and who built it ?
A page ranking algorithm created by Yahoo! which builds on PageRank.
1) Select trusted pages by hand (instead of equal estimates).
2) Trust is propagated to other pages by linking to them. One can also manually select spam pages.
3) The spam-likelihood propagates backwards: if a web-page is ‘closer’ to spam, it is less important.
What is BrowserRank and who built it ?
A page ranking algorithm created by Microsoft which is even more sophisticated than PageRank or TrustRank.
A web link graph is not a reliable data source for computing page importance, bc two different links on the same page may not be equally important.
Many websites could link to an important page, but if the users never click it, is it really important ?
Browser Rank takes into account the user’s browsing behaviour.
FB and YouTube are ranked much higher under BrowserRank.
