Displaying NotebookML Using CSS
NotebookML can be displayed in many current generation browsers, by using CSS style sheets. For example, Internet Explorer 5 or later and Netscape 6 or later have built-in support for CSS. CSS can even mimic the behavior of Mathematica's environments (like Working, Printout, Presentation, and so forth). To save a notebook as NotebookML with a Cascading Style Sheet, use the Export function, with a conversion option of "StyleSheets" pointing to the relevant stylesheet. Here is an example.
If you save a notebook as NotebookML and CSS (instead of simply converting it to HTML), the resulting file can be rendered in a web browser. The advantage of this approach is that you only need to create a single document, which can be viewed either in web browsers or in Mathematica. A non-Mathematica user can view the document in any web browser. But a Mathematica user will be able to open and edit the document as a notebook, evaluate the input, manipulate the graphics, and so on.