Rand Fishkin and Jeff Pollard from SEOMoz.org have released a 2007 Search Engine Ranking Factors Guide. Built on the collaborative wisdom of 36 search marketing experts, the guide references various elements or techniques found within five general areas of SEO knowledge.

The guide lists the 10 most positive and 10 most controversial ranking factors, adding a shorter list of the Top 5 negative factors. Contributors were asked to rate positive and negative SEO factor on a scale of 1-5 (with 5 being strongest). An added feature measures the level of agreement between all respondents. Comments from contributors can be found beside each factor.

According to the 36 experts, the Top 10 Positive SEO Factors are:

1. Keyword Use in Title Tag
2. Global Link Popularity of Site
3. Anchor Text of Inbound Link
4. Link Popularity within the Site’s Internal Link Structure
5. Age of Site
6. Topical Relevance of Inbound Links to Site
7. Link Popularity of Site in Topical Communities
8. Keyword Use in Body Text
9. Global Link Popularity of Linking Site
10. Rate of New Inbound Links to Site

The Top 5 Negative Factors are:

1. Server is Often Inaccessible to Bots
2. Content Very Similar or Duplicate of Existing Content in the Index
3. External Links to Low Quality/Spam Sites
4. Duplicate Title/Meta Tags on Many Pages
5. Overuse of Targeted Keywords (Stuffing/Spamming)

SEOMoz did a similar (though smaller) study in 2005. Back then, the Top 10 Positive Factors were:

1. Title Tag - 4.57
2. Anchor Text of Links - 4.46
3. Keyword Use in Document Text - 4.38
4. Accessibility of Document - 4.3
5. Links to Document from Site-Internal Pages - 4.15
6. Primary Subject Matter of Site - 4.00
7. External Links to Linking Pages - 3.92
8. Link Popularity of Site in Topical Community - 3.77
9. Global Link Popularity of Site - 3.69
10. Keyword Spamming - 3.69

At the end of the guide is a bonus section where respondents were asked four questions specifically about Google. While there was very little disagreement between the experts in the main part of the survey, there was quite a bit more when it came to questions about Google.

When asked an opinion on the controversial Google Sandbox effect, 38% said it was more prevalent than it was 6 – 12 months ago while 32% said the Sandbox Effect has never existed. A further 21% said it does exist but is less prevalent than it was 6 – 12 months ago while 9% said there was little change in the past 6 – 12 months.