Here is an article from "Copyright Axandra.com - Web site promotion software"
Off-site optimization refers to the ranking factors that are usually out of your control.
The most important off-site factor are the links to your web site:
Search engines determine the position of your website in the search results based on the on-site and the off-site factors of your website. What is more important for your website?
- The number of backlinks that point to your website.
- The quality of the backlinks that point to your website.
- How often your website is bookmarked on social bookmark sites.
- How often your website is mentioned on services such as Twitter.
Some webmasters invest most of their time in on-site optimization. Others swear that links from other websites are the only way to get high rankings on Google.
Depending on the keywords for which you optimize your website, you can achieve good results with both methods. You will get the best possible results for your website, if you combine both factors.