Responsive Web Design, or more simply: RWD is a standard for creating websites and web applications that automatically adapt to the screen size of the device on which they are displayed. RWD is a response to the needs of modern users, who increasingly use mobile devices such as phones and tablets to browse the Internet. As a result of adapting a website to smaller displays, aspects such as its appearance, layout and, sometimes, functionality change.
Websites that have not been developed in line with the idea of responsiveness display incorrectly on small devices or present content that is illegible for internet users. This problem can be eliminated by appropriately modifying the HTML and CSS code of the website. A popular method of creating portals in the RWD standard is the use of frameworks or libraries (e.g. Bootstrap), which significantly simplify the entire creative process.
Nowadays, whether a website is adapted for viewing on mobile devices is an important ranking factor that has a bearing on its visibility in search engines.