The World Wide Web Consortium (W3C) created a set of standards so the Web would work better for everyone. New browsers, mainly, support these standards; old browsers, mainly, don’t.

Prior to the creation of these standards (and prior to browser support for them), designers had no choice but to design and develop their sites according to the proprietary quirks of each browser; a method of working that has at least four major disadvantages:

1. It makes the internet inaccessible to people with disabilities.

2. It causes sites to fail in some browsers, and stop working as browsers changed.

3. It makes sites cost more than they had to, since designers spent so much of their clients’ money writing “workaround” code.

4. And by fusing presentation (design) and structure (content), sites became difficult to transport to wireless and other alternative devices. By contrast, with valid XHTML and CSS, it is relatively easy to generate wireless markup versions on the fly.