There are many legal aspects to starting a business, many of which vary signficantly, based upon exactly what kind of product or service is being provided, where it is being offered, etc.
Here are a few of the most common legal steps/issues that are faced by many web based businesses:
1) Business license - it is necessary to obtain a business license from your local jurisdiction
2) Business entity - it is not a legal requirement to form a business entity, such as a corporation or a limited liability company (LLC) in order to do business, but it is a very good idea in most cases, both to reduce liability and, potentially, for tax reasons as well. What type of business entity is best will depend on a number of factors, including who is involved in the business, how it will be funded, and what the owners' exist strategy for the business will be.
3) Sales and Use Taxes - Consult with a business CPA to ensure you are properly set up to pay any applicable sales and/or use taxes that may apply to the sale of the business' goods or services.
5) Ensure PCI compliance - If you will be accepting payments via credit card (either online, in person, or via phone), you will need to ensure that your handling of sensitive customer data, including credit card numbers, applies with Payment Card Industry (PCI) standards for data gathering, handling, security, and destruction.
There are many more legal issues that may apply to you business in addition to the ones listed above. It is a wise move to consult with qualified, experienced business attorney in your jurisdiction who can gather more information about your business and give you comprehensive advice and assistance in dealing with the wide range of legal issues that may apply to your business in particular.
DISCLAIMER: Please note that this response is not intended to and shall not create an attorney-client relationship with Briskin, Cross & Sanford, LLC or Byron M. G. Sanford, Esq. and are not intended to address the particular situation or circumstances identified int he question to which this response is offered. This response is not intended to serve as legal advice or counsel and is offered solely for educational purposes. Also note that I am licensed to practice law only in the state of Georgia. The information contained in this post is not intended to address any issues which may arise under the state or federal laws applicable to any state other than the state of Georgia.