Senior web developers design and create websites, as well as other online applications, which requires knowledge of programming languages, UI/UX principles, graphic design, and search engine optimization. In addition to their web development duties, senior web developers are often responsible for training junior web developers In today’s digital age, virtually every com employment in any industry. Some specialize in certain industries, while others work for firms that have clients across many industries. Most senior web developers work in a traditional work environment.