W3C (www (world wide web) consortium) develops standards and recommendation on how the web should be used. Part of the W3C remit is to recommend how information should be presented to end users in a format that includes as many users as possible. That basically means accessibility standards, things like allowing your content to be reviewed in different font sizes, picture tagging, voice browser compatibility and more.
W3C is not the only organization that defines standards for its users, governments, agencies and various charities define their own standards, and not all organizations that define the recommended standards follow them themselves (generally due to budgetary constraints).
Standards are defined to catch all issues so they won't be suitable for everyone's requirements especially when it comes down to design requirements. Strict W3C compliance often restricts creative design and sometimes both items are mutually exclusive – however the Minuco deign team does its best do accommodate both creativity and adherence to rules, when strict rules are required.