Technologies used in creating mobile-responsive websites include HTML5, CSS3, and JavaScript, which enable adaptive layouts and functionalities. Responsive web design employs media queries to adjust the layout, font size, and images based on the user's device and screen size. This ensures optimum user experience across various devices, from desktops to smartphones. Additionally, frameworks such as Bootstrap and Foundation offer pre-built components that simplify the development of mobile-friendly websites, enhancing speed and design consistency.