By experimenting and testing you can change your strategy based on data, facts and figures rather than someone's gut feeling or unsubstantiated opinion. With modern web analytics tools you can run experiments live on your website and allow your user or customer base decide for you based on click data collected on your site. For example does the "pay now!" banner convert more when it's size A than when it's size B?
By running experiments and testing you will be able to test various ideas without committing huge amounts of resources to it, this allows you to fail faster, but this is a good kind of failing, it means you won't commit all your resources to an idea that just is not going to work, rather you are able to quickly move onto the next idea to test.