In 2016, we could probably no longer imagine life without the World Wide Web. Advances in web technologies have enabled the development of complex web applications that solve the issues of billions of users on a daily basis. These users connect to the World Wide Web using all types of devices making it necessary to ensure that all websites work properly on a broad as possible spectrum of devices. In our diploma thesis we have described the strategies and best practices that enable the development of these adapted websites. We have presented in more detail the means of creating a responsive website design and how to ensure its usability, as well as the accessibility of the website. We have furthermore dealt with the aspect of a website’s sustainability, which, in a time when web technologies are developing so quickly, is very important. In the last part of our diploma thesis we have focused on the performance capabilities of websites, which are vital for providing its users with a good user experience.