HTML 5 is the new standard for building web applications that provides semantic structure and support for multimedia. It introduces useful new elements like <header>, <nav>, <article>, and <section> to replace non-semantic <div> tags. New features like <video>, <audio>, and the <canvas> element allow embedding multimedia content. While still evolving, many CSS 3 features can be used now like rounded corners, drop shadows, and new input types to create eye-catching designs. HTML 5 is not fully supported by all browsers yet, but continues advancing to become the standard for building modern web applications and sites.