Z-Index
Z-index is a CSS property that controls the stacking order of positioned elements on a web page along the z-axis (depth). It determines which elements appear in front of or behind others when they overlap, with higher values bringing elements to the front. This property is essential for managing visual layering in complex layouts, such as modals, dropdowns, and tooltips.
Developers should learn z-index when building interactive web interfaces where elements overlap, such as creating modal dialogs, dropdown menus, tooltips, or complex animations. It's crucial for ensuring that important UI components remain visible and accessible, preventing visual conflicts in multi-layered designs. Without proper z-index management, elements can appear in unintended orders, breaking user experience.