For simple Websites to complex web applications , Front-End/UI development is very crucial, "If UI fails Everything fails" . Mobile UI ,Tab UI,Web UI ,Responsive UI . Practically very few out there who masters the Front-End Development concept. It's not just HTML , nor Programming language like php. Few people have commanding knowledge over DOM,BOM,Javascript ,Javascript Frameworks , AJAX and JSON . Having knowledge to connecting them to Back-end or programming modules.