jsFiddle is the perfect solution; it provides a custom environment (based on user selections) to test (or fiddle with) your JavaScript, HTML, and CSS code ... list provides a sample of the ...

The jury is still out if a Turing machine is possible, but he did manage to generate some simple fractals using just CSS and HTML, no JavaScript required. Most fractals are recursive, and CSS ...

Essentially, we get a more granular HTML syntax, which can just load segments instead of whole pages, and can submit Ajax requests. This is an interesting example of the DRY principle in action.