Search engine marketing optimization is critical to obtain the best possible return on investment. There are many factors to consider when marketing via a search engines pay per click platform.

Many factors are within your control to test, analyze and optimize, while other factors are not. Whether your competitors bid on the same keywords, what price they are willing to pay, changes in customers search behavior, changes in industry terms or new features, and other factors may be out of your control. It is possible depending on how you set up your campaign that your daily spend can vary greatly. You may even lose all traffic and not obtain visitors on a particular given day due to factors beyond your control.

Not only do you need to test every possible variable such as the advertisements, time of day, geographic targeting, mobile devices, landing pages, keywords, and many more, but you need to constantly watch the campaigns closely to assure you are maximizing your return on investment.

I wrote about this topic more extensively here.