Resources on the Web are identified by Uniform Resource Identifiers (URIs), and can be accessed using web protocols such as HTTP. A resource can have several representations varying along a set of dimensions, forming a set of variants. Content negotiation (CN) is the mechanism for selecting the appropriate variant that conforms to a set of preferences (constraints). Over the years, various dimensions of CN, styles of CN, as well as ways to convey constraints have emerged to satisfy new requirements and solve new use cases. This demo presents a new resource called Content Negotiation Theoretical Framework (CNTF): a website that collects knowledge about CN use cases, styles, dimensions, etc., and organises it according to an ontology. CNTF aims to highlight existing solutions, if available, or suggest plausible ways to satisfy common requirements. It is intended to be used to disseminate our future proposals for advancing CN, making it a sustainable and up-to-date digital survey of CN.