Google has a market share of 73.32%, followed by Yahoo with 15.78%. Ask.com has 3.93%, MSN Search 3.52% and Live Search 2.11%.
Google is obviously still dominating here and Yahoo is doing a little better then they used to. Plus now MSN is now BING.com and they are doing a very aggressive marketing campaign and Im sure they will be moving up in these results soon. Its key to have your web site optimized mainly for Google but you should also make sure it comes up at Yahoo and Bing.
Google optimization is huge. It should definitely be one of the main focuses for anyone building a website that wants to get traffic. If it wasn’t for Google, I wouldn’t be where I am today.