Amaya might be of interest.
It's the W3C's reference browser implementation, with equal emphasis on creation and viewing. To quote:
"Amaya is a Web editor, i.e. a tool used to create and update documents directly on the Web. Browsing features are seamlessly integrated with the editing and remote access features in a uniform environment. This follows the original vision of the Web as a space for collaboration and not just a one-way publishing medium."
Last time I tried it (several years ago), it would regularly crash, but it's enough to open your eyes as to what might be.
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Edit: I should add a further quote: "It's development is stopped." Whilst it's not realistic to use Amaya, it would be great if its model inspired others.