Why Does CSS Work with Non-Standard HTML Elements?

Why CSS Interacts with Non-Standard Elements

While creating custom elements, some may notice that CSS effectively styles elements that are not part of the standard HTML specification. This can be puzzling, as one might assume CSS only supports recognized elements. Understanding the underlying mechanism and the reasons behind why one should avoid using such elements can shed light on this phenomenon.

Reason for CSS Compatibility

Browsers are designed to be forward-compatible to some extent. When a new HTML element is introduced, CSS, JavaScript, and ARIA can emulate its behavior in legacy browsers. This requires that the unregistered element appears in the DOM, enabling these languages to manipulate and add functionality.

Avoidance of Non-Standard Elements

Despite their functionality, professors typically advise against using non-standard elements due to several factors:

• Violation of HTML Specification: They are not formally allowed by HTML, which can lead to validation errors or unexpected behavior.
• Conflict Potential: In the future, elements with similar names may be introduced as part of the HTML standard, potentially overriding the functionality of custom elements.
• Alternative Solutions: Existing HTML elements often suffice for the intended use, providing a more reliable and standardized approach.

Professor's Lack of Knowledge

It is not uncommon for professors to be unaware of the compatibility of CSS with non-standard elements. This may be because such elements are seldom used due to their aforementioned drawbacks. Additionally, technology evolves rapidly, and not all professionals stay abreast of all the latest developments.

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