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 ...

For example, you can use an image as a clicking button for a particular link. The problem is that the browser displays a border around this image. To remove the border in HTML/CSS, you need to change ...

Business apps built with web technologies, particularly HTML, CSS, and JavaScript ... a big sections on providing structured data examples. HTML is often recommended as a nice introduction ...

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.