Generate a detailed outline for a high-converting landing page structure, suitable for a 500-word article.  The outline should cover the essential sections of a landing page, including but not limited to: headline, subheadline, hero image/video, value proposition, social proof (testimonials, case studies, logos), features and benefits, call to action (CTA) button, and contact information.  For each section, provide best practices for copywriting, design, and user experience (UX).  Consider different landing page types (e.g., lead generation, sales, webinar registration) and how the structure might adapt for each.  The outline should be structured as a numbered list, with each section clearly defined and explained.  Include examples of successful landing page structures from well-known companies.  The article should also address A/B testing strategies to optimize the landing page&#8217;s performance.  Finally, briefly discuss the importance of mobile responsiveness and SEO optimization for landing pages.