SEOMoz, industry leading SEO company releases a list of factors that contribute most ranking a website on major search engines every year. SEOMoz Ranking Factors was compiled through interviewing with around 100 industry leader and experts with a hundred identified SEO factors and have them rate and comment on these factors. They have recently released SEOMoz Ranking Factors 2009, with some of the highlights below:

Top 5 Ranking Factors:

1. Keyword Focused Anchor Text from External Links
2. External Link Popularity (quantity/quality of external links)
3. Diversity of Link Sources (links from many unique root domains)
4. Keyword Use Anywhere in the Title Tag
5. Trustworthiness of the Domain Based on Link Distance from Trusted

Top 5 Negative Ranking Factors:

1. Cloaking with Malicious/Manipulative Intent
2. Link Acquisition from Known Link Brokers/Sellers
3. Links from the Page to Web Spam Sites/Pages
4. Cloaking by User Agent
5. Frequent Server Downtime & Site Inaccessibility

Top 5 Most Contentious Factors:

1. Cloaking by Cookie Detection 16.3% strong contention
2. Cloaking by JavaScript/Rich Media Support Detection 15.4% moderate contention
3. Hiding Text with same/similar colored text/background 15.3% moderate contention
4. Cloaking by IP Address 15.3% moderate contention
5. Cloaking by User Agent