The use of the internet is rapidly increasing nowadays, and people are now doing all kinds of transactions online. Therefore, it is of great importance for websites to be mobile-friendly and responsive. Responsive web design is a design method that enables websites to be displayed seamlessly on different devices (computer, tablet, smartphone, etc.) with different sizes and screen resolutions.\n\nMobile-friendly websites are websites that are designed to be easily used on mobile devices and are tailored to the screen sizes of mobile devices. Mobile-friendly websites provide a better user experience for mobile device users, and therefore, mobile-friendly websites are of great importance today.\n\nThe importance of responsive web design and mobile-friendly websites can be viewed from many different angles. For businesses, responsive web design and mobile-friendly websites provide a better user experience for their customers, thus increasing customer satisfaction. Additionally, mobile-friendly websites provide easier access for mobile device users.\n\nResponsive web design and mobile-friendly websites are also of great importance in terms of SEO. Google prioritizes mobile-friendly websites in its listings, and therefore, mobile-friendly websites provide a significant advantage in terms of search engine optimization. Additionally, responsive web design enhances the user experience of websites on different devices, which is also important for search engine optimization.\n\nIn conclusion, responsive web design and mobile-friendly websites are of great importance today. For businesses, they increase customer satisfaction and provide easier access for mobile device users. Additionally, they provide a significant advantage in terms of search engine optimization. Therefore, having responsive and mobile-friendly websites has become a necessity today.