Google has mentioned in the past that it has 200 separate ranking factors for evaluating the relevance of a web page to a keyword (the "Google Algorithm"). But SEOs trying to reverse engineer ranking factors is like trying to peek at the man behind the curtain with tweezers...through multi-variate testing and other empiric methods, we can make changes to websites and monitor the search results, but only broadly guess at which changes carry the most weight or have any effect at all.
Darren Revell of Recruitwise Technology threw down a challenge on the Search Engine Land discussion group on Linked In, challenging it's members to identify all 200 ranking factors. A heated discussion followed, which identified most, if not all, commonly accepted factors. After a week of discussion, Darren summarized the results:
1 Search terms in the HTML title tag?
2 Search terms in the HTML body copy?
3 Search terms in bold typeface?
4 Search terms in header tags?
5 Search term in anchor text in links to a page?
6 PageRank of a page (the actual PageRank, not the toolbar PageRank)?
7 The PageRank of the entire domain?
8 Quality of link partners?
9 Type of back links that bring anchor text juice for search terms?
10 The speed of the web site
11 Search terms in the URL - main URL and page URLs ?
12 Search term density through body copy (About 3 - 5%?) ?
13 Fresh content ?
14 Good internal linking structure ?
15 Age of the domain ?
16 Links from good directories ?
17 Image names ?
18 Image ALTs ?
19 Reputable hosting company
20 Diversity of link partners
21 Geo located results
22 Rate of new inbound links to your site ?
23 Relevance of inbound links - subject specific relationship with target page negative factors too:
24 Pages 404s, 414s etc ?
25 Duplicate title/keywords
26 Participation in link schemes
27 Search Terms the First Words of the Title Tag ?
28 Search Terms in the Root Domain Name (searchterm.com) ?
29 Search Terms in the Page Name URL (e.g. acme.co.uk/folder/searchterm.html) ?
30 Search Terms in the Page Folder URL (e.g. acme.co.uk/searchterm/page.html) ?
31 Search Terms in the First Words in the H1 Tag ?
32 Search Terms in other Headline (H) Tags ?
33 Search Terms in Internal Link Anchor Text on the Page ?
34 Search Terms in External Link Anchor Text on the Page ?
35 Search Terms in the First 50-100 Words in HTML on the Page
36 Search Terms in the Page’s Query Parameters (e.g. acme.co.uk/page.html?searchterm) ?
37 Search Terms in the Meta Description Tag
38 Social graph fans
39 Social graph fans earned impressions
40 Social graph fans earned impressions with links
41 Secondary fan connection citations earned impressions
42 Otherme citation (social media linking) ?
43 Rich snippet geo-reference ?
44 Rich snippet UGC rating ?
45 Placement of backlinks in page ?
46 Quantity of backlinks ?
47 Quantity of linking root domains ?
48 Quality of linking root domains ?
49 Link distance from higher authority sites ?
50 Outgoing followed links from back linked pages
51 Country specific domain ?
52 Domain classification of linking domains ?
53 Domain sculpting
54 Redirect permanent (not 302) ?
55 Page accessible ?
56 Sitemap_Index/Sitemap limit 10K ?
57 Sitemap folder geotargeting
58 Index/Follow ??And the more controversial ?
59 Bounce rate (personalization) ?
60 Visits (personalization) ?
61 Visits (scraped from Alexa) ?
62 Semantic relevance (synonym for matching term) ?
63 Reputation/advocacy (positive chatter)
64 URL length ?
65 Frequency of Updates ?
66 Domain Name Extension Top Level Domain - TLD ??# Some -Ve factors, as: ?
67 Link to a bad neighborhood ?
68 Redirect thru refresh metatags ?
69 Poison words ?
70 Keyword stuffing threshold ?
71 Keyword dilution ?
72 Dynamic Pages ?
73 Use of Frames ?
74 Gateway, doorway page
75 Keyword saturation (Saturation levels do play a crucial role in the ranking of your pages) ?
76 Traffic buying (effect adversely)
77 Link buying (effect adversely)
78 Over optimization - There is a penalty for over-compliance with well-established, accepted web optimization practices. ?
79 Excessive cross linking (effect adversely) ?
80 Linking between all the domains hosted on same IP (This one may be debatable) ?
81 Hidden content (effect adversely) ?
82 Cloaking (effect adversely) ?
83 Excessive use of graphics (effect adversely) ?
85 Comment spamming (effect adversely) ?
86 Title attribute of link ?
87 Sitemaps: XML, Text, HTML (XML Sitemap (Aids the crawler but doesn’t help rankings) ?
88 W3C compliant html coding
89 Duplicate content on site (effect adversely) ?
90 Duplicate tags on site (effect adversely) ?
91 Page file size/load time ?
92 Number of links on page (too many will effect adversely) ?
93 Video header and descriptions ?
94 Video sitemap
95 Quality content
97 IP address range (many are blacklisted for spamming) ?
98 Whether the site has been previously de-indexed due to malpractice
99 Relevance of title tag to page content ?
100 Relevance of META Description to page content
101 Code-to-text ratio
102 Canonical URL
103 Directory depth
104 Querystring param count
105 An active adsense campaign. We have noticed our page rank higher when we are also running an active adsense campaign.
107 keyword spamming
108 multiple domains to same website
109 link structure - do you link to '/', 'index.htm'
111 Quality & Number of Blogs
112 Authority ranking of subject matter
113 Link attributes - like rel=nofollow
114 Use of WebmasterTools
115 Popularity (no one seems to have mentioned this one before?)
116 Brand recognition
117 Linear Distribution of Search Terms on the html
118 IP address link to be varied, not from the same server which have lower link juice
119 Standard Deviation of Search Terms in the Population of pages containing Search Terms
120 URL shortener
123 Mobile accessibility
124 Synonyms , language, query terms
125 Page category
126 SERP click thru rate. Say your website ranked #1 for "bike shoes" keyword phrase but 60% off the traffic went to website in the #2, I guarantee you Google will notice and would make an adjustments.
127 Relevance. (to searched phrase)
128 Comprehensive. word-count and pages of content on topic to top keyword of entire site along with relevent named images, videos, news, with top keyword
129 Fresh. Latest page updates with accurate sitemap so googlebot re-checks your site frequently.
Domain / server factors
130 Domain age;
131 Length of domain registration;
132 Domain registration information hidden/anonymous;
133 Site top level domain (geographical focus, e.g. com versus co.uk);
134 Site top level domain (e.g. .com versus .info);
135 Sub domain or root domain?
136 Domain past records (how often it changed IP);
137 Domain past owners (how often the owner was changed)
138 Keywords in the domain;
139 Domain IP;
140 Domain IP neighbors;
141 Domain external mentions (non-linked)
142 Geo-targeting settings in Google Webmaster Tools
143 Domain registration with Google Webmaster Tools;
144 Domain presence in Google News;
145 Domain presence in Google Blog Search;
146 Use of the domain in Google Analytics;
147 Server geographical location;
148 Server reliability / uptime
149 Page internal popularity (how many internal links it has);
150 Page external popularity (how many external links it has relevant to other pages of this site);
151 Number of visits;
152 Visitors’ demographics;
153 Bounce rate;
154 Visitors’ browsing habits (which other sites they tend to visit)
155 Visiting trends and patterns (like sudden spiked in incoming traffic.
156 How often the listing is clicked within the SERPs (relevant to other listings)
157 Use of Google Check out on your site
158 Domain name is one of the important factors that give good page ranking in that particular sector.
159 Compression for size by eliminating white space, using shorthand notation, and combining multiple CSS files where appropriate. GZIP can be used.
160 You can use CSS sprites to help to consolidate decorative images.
161 No redirection to other URLS in the same server through flash banner images
[Factors marked with a "?" are subject to dispute as to their importance]
The sheer number of identified factors is overwhelming at first, but also shows how interrelated many ranking factors are. Improving your title tags, for example, will address many individual ranking factors at once, as would targeting inbound links from websites with good reputation and relevant content to your own website. Publishing content for syndication, when done properly, will create many positive factors as well. And of course there are negative factors to avoid, which would reduce relevance.
All in all we came up with approximately 80% of Google's ranking factors...but like the recipe for Coca Cola, the rest are some of the search industry's most tightly guarded secrets. And one can assume many unidentified factors are weightings between groups of individual factors. Will we ever know Google's secrets? All we can continue to do is test and measure, and slowly build up the empirical evidence that will point to the rest.
Thanks everyone for the inspiration and collaboration...knowledge is search-rank power!