When selling auto parts online, ensure compliance with all federal, state, and local regulations. This includes understanding and adhering to environmental regulations, safety standards, and import/export laws. Ensure the parts are genuine, properly labeled, and meet safety standards. Provide clear return policies and warranties. Also, comply with consumer protection laws, data privacy regulations, and proper disposal practices for hazardous materials. It's advisable to consult with a legal expert to ensure full compliance with all relevant laws and regulations to avoid legal issues.