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Modern front-end development has evolved from simple document layout to complex application architecture. This guide covers the "Holy Trinity" of the web: HTML5 for semantic structure, Modern CSS (Flexbox, Grid, Variables) for responsive layout, and ES6+ JavaScript for interactivity and logic. :root --primary-color: #3498db
While modern frameworks abstract direct Document Object Model manipulation, mastering native API methods like querySelector and addEventListener remains crucial for debugging and optimization. Modern CSS (Flexbox