The concept can be applied to entire systems, electrical interfaces, telecommunication signals, data communication protocols, file formats, and programming languages.
[citation needed] HTML is designed to treat all tags in the same way (as inert, unstyled inline elements) unless their appearance or behavior is overridden; either by the browser's default settings, or by scripts or styles included in the page.
One case where this did not work as intended was script and style blocks, whose contents are meant to be interpreted by the browser instead of being part of the page.
There may be backward compatibility for better marketability (such as a DVD player playing an audio CD), but it is not intrinsic to the standards.
Immediately, the sales manager calls "NUC" and the problem is understood: if the footprint changes and existing customers are considering buying more from the producer, they will have to fit a different sized unit in an office designed for the 4 foot square cubicle.