SEO for Google Yahoo and MSN

What is the difference of SEO between Google yahoo and MSN
No doubt google is the number one search engine on the web.
And lots of traffic comes from google.It means that
Google search engine optimization is a deciding factor for your
web site success.Means concetrate more on Google.
Consider even a minute thing for Google optimization.

But by the time dont forget Yahoo and MSN search engine optimization too.
If you have 6 web pages in your web site.
Divide it like this, optimize two web pages for google.
Two page for yahoo and rest two pages for MSN.
There is an advantage of such type of search engine optimization
By the time your site will get listed in Google ,the traffic will come from Yahoo
and MSN.So it keeps your business alive.