The quest to transform the television viewing experience into a digital media service is happening thanks to the addition of companion screens to the TV. Multi-device experiences become more intuitive and easier to use federating cooperative devices. They also bring new creative opportunities to schedule and distribute interactive content synchronised with the TV programme through any connected screen. The rise of HTML5 to develop responsive applications across multiple devices adds a significant amount of improvement enabling universal delivery. A key challenge to harness the power of navigation engaged with the story on the TV is the responsive design of a unique application spanning all the available screens. This paper presents user tests in order to explore the relevant parameters to create responsive User Interfaces for Web-based multi-device applications driven by media content.