Google’s Special Algorithm Factors include a user’s browser’s history and Search History.
1. Query Deserves Freshness: Google gives newer pages a boost for certain searches.
2. Query Deserves Diversity: Google may add diversity to a SERP for ambiguous keywords, such as “Ted”, “WWF” or “ruby”.
3. User Browsing History: Sites that you frequently visit while signed into Google get a SERP bump for your searches.
4. User Search History: Search chain influence search results for later searches. For example, if you search for “reviews” then search for “toasters”, Google is more likely to show toaster review sites higher in the SERPs.
5. Geo-Targeting: Google gives preference to sites with a local server IP and country-specific domain name extension.
6. Safe Search: Search results with curse words or adult content won’t appear for people with Safe Search turned on.
7. Google+ Circles: Google shows higher results for authors and sites that you’ve added to your Google Plus Circles
8. DMCA Complaints: Google “downranks” pages with DMCA complaints.
9. Domain Diversity: The so-called “Bigfoot Update” supposedly added more domains to each SERP page.
10. Transactional Searches: Google sometimes displays different results for shopping-related keywords, like flight searches.
11. Local Searches: Google often places Google+ Local results above the “normal” organic SERPs.
11. Google News Box: Certain keywords trigger a Google News box:
12. Big Brand Preference: After the Vince Update, Google began giving big brands a boost for certain short-tail searches.
13. Shopping Results: Google sometimes displays Google Shopping results in organic SERPs:
14. Image Results: Google elbows our organic listings for image results for searches commonly used on Google Image Search.
15. Easter Egg Results: Google has a dozen or so Easter Egg results. For example, when you search for “Atari Breakout” in Google image search, the search results turn into a playable game (!). Shout out to Victor Pan for this one.
16. Single Site Results for Brands: Domain or brand-oriented keywords bring up several results from the same site.
Here is a complete overview of Google’s Algorithm Factors.