This two-part certification is designed for those who have previous experience crafting website pages, templates, and styles and who are proficient in HTML and CSS. HubSpot Design Certification tests the knowledge of and proficiency with the template design tools in HubSpot's Content Optimization System. The HubSpot Content Optimization System, or COS, is a system that blends content and context to create rich, personalized experiences for everyone viewing your blog, website, landing pages, and emails.