http://www.stillbreathing.co.uk/2014/04/08/progressive-enhancement
This is the crux of progressive enhancement. Here’s the recipe:
Start with a basic web page that functions with nothing but the HTML, using standard semantic mark-up. Yes, it will require full-page GET or POST requests to perform actions, but we’re not going to stop there – we’re going to enhance the page.
Add CSS to style the page nicely; go to town with CSS3 animations if you want
Add JavaScript to enhance the UI and provide all the modern goodies: AJAX, client-side models, client-side validation etc
The benefits are obvious:
If the JavaScript or CSS files (or both) fail for any reason whatsoever the page still works
The use of semantic HTML means the page is fully understandable by search engine spiders
Because everything is rendered in HTML, not built up in JavaScript, it is understandable immediately by assistive devices
Serving fully-rendered HTML is quicker than building that same HTML client-side
Built-in support for older – and newer – browsers and devices
The best web developers on the planet all argue that progressive enhancement is the best way to approach web development. I honestly have no idea why anyone would think otherwise. There’s a good article (it’s actually the first chapter of Filament Group’s “Designing With Progressive Enhancement” book) on the case for progressive enhancement here.
