Generate a detailed outline for a 500-word article explaining the optimal structure of a high-converting landing page.  The article should cover the key elements of a successful landing page, including above-the-fold content, clear value proposition, compelling headline, strong call-to-action (CTA), social proof, and effective use of whitespace.  Discuss different landing page variations (e.g., lead generation, sales, webinar registration) and how their structure might differ.  Include best practices for mobile responsiveness and A/B testing to optimize conversion rates.  The article should be targeted towards small business owners and marketers with limited web design experience.  Focus on practical advice and actionable steps, avoiding overly technical jargon.  The final output should be structured as a numbered list of sections with concise headings and a brief description of the content for each section.  Success will be measured by the clarity, completeness, and practical applicability of the outline; it should provide a clear roadmap for writing a comprehensive and useful article on landing page structure.