Over 80% of the Internet's users go to a search engine before reaching a web site.When someone types your product or service's key words into a search engine if the site lists in the first page then chances are there that the user might visit the website.In short SEO is the best way to promote site and gain your desired web presence.The factors that Google considers are keywords in URL, Title, Text, Domain age,Number of visitors etc.It keeps updating the factors for page ranking. The companies that provide SEO also should update accordingly.If we get services from such a concerned company then we can definitely make SEO to be effective.I have used the SEV(Search Engine Visibility) from XnYnZ.com as they provide keyword and suggested topics,submit the site to over 100 search engines and also provide reports which eventually improved my website traffic.