When it comes to SEO many people make the mistake of thinking that search engine optimization as an action. They are wrong. SEO is a process that must be continually maintained for as long as you wish your website to competitively rank for certain keywords.
Imagine you had purchased a car with the intention of racing. You then spent a great deal of time; money and effort in upgrading that car competitively. After many performance upgrades you take it to the tracks and enter it to compete against millions of other cars of varying performance and experience. You do not however invest in a pit crew or a maintenance crew. Would you realistically expect your car to come in first place? You do not get new tires, or fuel or any of the other equipment and services needed to keep your car operational let alone competitive. You do however continue to enter your car in the race. Months later, when you check on its performance how surprised would you be to find out that its doing even worse in those races then when it started?
Search Engine Optimization (SEO) works the same way. The car is your website, the performance upgrade is SEO and the pit crew is progressive optimization.
SEO maintenance is the continued optimization of your search engine marketing campaign. The internet is constantly undergoing changes as is the algorithms used to prioritize websites rankings within the search engines.
There are many factors used by search engines to determine ranking. A major factor is the relevancy and authority of a subject related to keyword phrases. If your content is not being upgraded or updated then it stands to reason that your site content is less relevant then a competing site with up to date information.
Once you do obtain high ranking within the search engines, it is essential that progressive optimization is performed to keep those rankings. Make no mistake, your rankings will change. The search engines are constantly making changes to their algorithm which will affect the rankings for your keyword phrases. Sometimes this change will have a positive effect, often it will result in lower ranking. Sites have been known to disappear from search engine results entirely after an algorithmic change. It is important be aware of any such algorithmic changes and be prepared to counter any drop in ranking.
Another thing to keep in mind is that you and your competitors are all striving for the same rankings within the search engines. Your increase in rank comes at the expense of a competitors ranking. Remember your competitors are also trying to regain or improve their own search engine rankings as well. Without continually optimizing your own site, your competitors will overpass you and push your ranking results off of the first page, then off the second and so on.