The Principle Explained
If you open the browser’s View Source feature while viewing a web page, you will find a document that consists of all the words that appear on the page (the content). Thickly interspersed with those words, there are non-words, numbers, and symbols (the code). The code describes how the content should be formatted and what purpose it serves.
During the process of creating a web page, errors tend to creep into the code. In fact, mistakes are almost inevitable. These errors almost always affect the appearance and functionality of the page. The effects may be minor (the formatting is slightly off) or major (the page does not display at all).
Principle 4 is about making websites robust. A robust web page meets the following conditions:
- It displays content as the author intends
- It functions as the author intends
- It is compatible with current and future browsers, web-enabled devices, and assistive technologies
Browsers, web-enabled devices, and assistive technologies do their best to compensate for coding errors. But there are limits to what can be repaired. To conform to Principle 4, web authors are required to avoid specific kinds of coding errors.