Internet marketing refers to strategies used to promote and sell products or services online, including e-commerce, search engine optimization, social media, email marketing, and blogging. Common mistakes include paying for pop-ups, spamming emails, stale advertising without calls to action or poor placement. Effective long-term strategies involve participating in social media, online networking within niche markets, creating frequently updated blogs and articles, adding business listings to directories, and using keywords and search engine optimization.