In the "Partials" section,

The line :
Y.Handlebars.registerPartial('header', '<h1>Handlebars</h1>');

should actually be:
Y.Handlebars.registerPartial('header', '<h1>{{title}}</h1>');

This shows the inheritance of the context in partials.

In the example, the partial template should renders to "<h1>My Page About Mustaches</h1>"
With the provided code, it renders to "<h1>Handlebars</h1>"