I suggest that you construct easy to read tables and graphs for the financial portion of the plan. The worksheets suggested are: Salaries/Wages and Benefits, Outside Services, Insurance, Advertising Budget, Occupancy Expense, Sales Forecasts, Cost of Projected Product Units, Fixed Assets, Growth (or Start_Up) Expenses, and Miscellaneous Expenses. You may find some of the worksheet templates at PlanWare.org to be useful.
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.
Management and Operations: Because management problems are the leading cause of business failures, it is important to discuss management qualifications and structure. Resumes of the Principals should be included in supporting data. If your business will have few employees and rely heavily on outside professionals, list these key people and their qualifications. If you are seeking financing, include personal financial statements for all of the principals in the supporting data section.