Web development has significantly evolved from static web pages to dynamic web applications, enabling users to perform diverse activities online. However, developers often make common mistakes that can adversely affect user experience and website functionality. These include relying on non-responsive design, which can lead to poor display on various devices, and depending heavily on website builder tools, which may introduce excessive code and hinder performance. Using outdated HTML can also lead to compatibility issues with modern browsers, while inadequate input validation can result in incorrect user data submissions. Additionally, ensuring cross-browser compatibility is crucial, given the wide array of browsers and devices in use today. Addressing these issues with updated technologies and thorough testing can improve website quality and search engine rankings, making them more user-preferred.