Search Engine Optimization is a very important part of a web site. It includes several ever changing qualities. Dealing with these ever changing qualities on a weekly and even daily basis is the best way to keep up with the latest acceptable practices.
There are many settings that when used incorrectly, they can hurt your search rank compared to your competitors. Things like titles, urls, meta descriptions and content are big items to optimize on page SEO. Many other items deal with your overall website experience.