As far as the West is concerned Google is the main search engine that you need to be considering first for bringing visitors to your website. We have been working with Google since it began, it started trading just before we did and once it secured the AOL user base, it became popular very quickly for it’s speed and simplicity.
One of the first search engines - Yahoo! (known in 1994 as "Jerry and David's Guide to the World Wide Web") now provides the Bing search results (formerly Live Search, Windows Live Search, and MSN Search).
From an SEO point of view, you shouldn’t ignore these two search engines, they have a small (8%) reach, but they are growing whereas Google has experienced a reduction in their share of searches.
How dominant is Google in the UK?
The graph on the right shows the position in October 2012.
It is pretty clear that - at the moment - Google is still the search engine to understand and engage with. It is certainly where we spend most of our time when promoting websites for our clients.
Google regularly "resets" its results of searches. We see this about once every month on average but sometimes it happens more frequently. It is known in the SEO world as a "Panda Slap", as the updates and algorithms used are referred to as “Google Panda”.