On occasion, a UI drastically changes based on which features are available in a browser. A good example is drag and drop. When providing Help pages or other documentation for an interface, it seems helpful that the content should also change based on feature detection. One could do this in a very rudimentary way using just CSS:

/**
 * Hide the positive-outcome instructions by default.
 * Progressive enhancement and all..
 */
.faq.draganddrop {
  display: none;
}
 
/**
 * If .draganddrop tests positive when Modernizr executes, swap instructions out
 */
.draganddrop .faq.draganddrop {
  display: block;
}
.draganddrop .faq.no-draganddrop {
  display: none;
}

In this example, the first .draganddrop is the class on the <html> tag, and the second is a class on an individual Help node (or however you choose to set it up in Drupal).

However you choose implement the Help content, a Drupal module that enhances that content type would be a cool thing to have automatic support for.

This is something that I think deserves to be its own module, but I just wanted to jot the idea down and it would probably depend on the Modernizr module so filing the issue here made sense.