Once you have a plan in place, it's important that you follow it. If you're achieving your goals you should stick with the plan. If you are not achieving your goals then you will have go back, analyze your plan to find out what is working, what is not working and why it is not working. A plan is not etched in stone. It is subject to change. As time goes on, things change in this world and businesses like everyone else are subject to change. A good plan will reflect changes that a company has to make to keep it competitive and successful.
So, although a detailed business plan may not be required for an online business, I am going to include it here so you can at least look at and consider each section and determine yourself if it applies to your business.