SEOs have known for years that the major search engines use different algorithms to return search results. You can see this yourself by typing the same keyword(s) into different search engines and reviewing the results. You will see differences, sometimes significant, in the sites listed and their order.
Of course, search engines not only keep their exact algorithms secret, they make regular tweaks to them, so it’s impossible to know exactly what aspects of our Web sites are most important to their rankings. It is possible, though, to get an idea of what’s most important by doing identical searches in each engine and evaluating the sites that rank highest.
Keeping track of preferences for three major search engines was often confusing and headache inducing. Because Google gets the lion’s share of the search market, it was often the first choice to optimize for. Now that Microsoft and Yahoo have joined forces, life has gotten easier. Microsoft’s Bing will soon power Yahoo results, so we have only two algorithms to compare, and it is easier to see where the differences lie.
Inbound links: Google views links in to a page as independent, unbiased votes for a page. Therefore, the more links, the more favorably Google views the site. Link quality also matters, so links from a page with high PageRank (PR) are more helpful than ones from low PR sites.
Fresh Content: Supplying fresh, relevant content has been an SEO mantra for a while, because Google’s algorithm places a lot of emphasis on this. Bing seems less concerned with freshness, and often serves up older pages.
Page Rank: While Google downplays the importance of Page Rank, we know it does matter. High PR sites tend to rank higher in results, and, as mentioned, the higher the PR of a site linking to you, the greater benefit you get from it. Bing places little, if any, emphasis on this Google calculation.
Relevant anchor text: Bing cares less about the quantity of inbound links than does Google, but it places greater emphasis on the anchor text of those links. Strive for quality inbound links with relevant anchor text to satisfy both engines.
Outbound links: It’s never been clear if Google rewards outbound links, but it is clear Bing does. Links out to other authoritative sites provide extra value to visitors and a boost to your Bing ranking.
On-Site SEO: In recent years, on-site SEO factors have been considered a good idea but not critical, because Google emphasizes off-site factors, like backlinks. Bing may reverse this trend by rewarding sites with all the right meta tags, heading tags and solid internal linking.
Site Authority/Domain Age: Bing appears to prefer older domains or sites from authoritative organizations more than Google does. This could penalize new businesses or smaller sites.
The two engines do have different preferences, but many of them are things you should be doing anyway to provide a good user experience.