Modern CSS has evolved significantly, allowing developers to create advanced user interface patterns like scrollspy entirely without JavaScript. Traditionally, tracking which section of a page is currently visible required complex event listeners and observer APIs. However, newly introduced CSS features such as the `scroll-target-group` property and the `:target-current`, `:target-before`, and `:target-after` pseudo-classes enable browsers to natively understand and manage scroll markers. By combining these capabilities with advanced layout techniques like anchor positioning, developers can build smooth, continuous, and responsive tables of contents that adapt gracefully as users scroll through a document. While browser support remains limited primarily to Chromium-based engines, this approach exemplifies a progressive enhancement strategy that enriches modern web experiences.