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 ... one of the examples — Delayed ...

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.

Open an HTML document containing a DIV that references CSS classes. A typical DIV might appear as shown below: The content inside this DIV is blue The DIV in this example references a CSS class ...