As you fellow Internet marketers have heard many times, Google, Yahoo, and MSN are the three main search engines, and the main source of traffic for the majority of websites. It's a common misconception that you can only SEO a website for one or two of these search engines. To clarify, most SEO's and Internet marketers either aim for Yahoo and MSN, or just Google. They claim the differences in the algorithm, as well as the fact that Google gets most websites more traffic than MSN and Yahoo combined, is the motive behind their SEO strategy.
It is true that it's much harder to SEO for Google than for Yahoo and MSN combined. However, it's precisely the difference in algorithms and the disparity in traffic that has led me to believe that Tri-SEO is the way to go. It's very simple if you think about it.
First, because Google is simply the biggest source of traffic, and also the hardest to SEO, you make your website to Google's standards and let the time go by as you add content, feeds, and your PageRank Grows.
While this is happening, you SEO your other main pages so that you can get #1 positions for keywords/phrases in Yahoo and MSN. The point is that while Google takes it's time to consider your website an "Authority Site," you still get traffic from MSN and Yahoo. When the Google Dance starts, in your favor, you will end up with traffic from all three sources!
Source : http://www.ezinearticles.com/?Conducting-andquot;Tri-SEOandquot;-Successfully---Google,-Yahoo,-and-MSN&id=329252
