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W3.CSS Validation


CSS Validation

The W3C CSS Validation Service can be used to check the correctness (validity) of W3.CSS.

The Validation Service was created by the W3C to help Web developers validate CSS.


False Errors?

The W3C CSS Validator checks for CSS2 and CSS3 properties.

Some CSS properties are supported by most browsers, but not valid in the W3C standardization process.

W3.CSS uses some CSS4 properties that are supported by all modern browsers.

Below is a list of validation errors that should not stop you from moving forward.


The Property user-select

Why is this shown as an error?

The W3C CSS Validator checks for CSS2 and CSS3 properties.

The user-select property is defined in the CSS4 Draft.

The user-select property has been supported by all modern browsers for some time now.

The user-select property is important to modern web applications.

It controls how (or if) the text in an element is allowed to be selected.

Read More ...


The Property pointer-events

Why is this shown as an error?

The W3C CSS Validator checks for CSS2 and CSS3 properties.

The property was a part of the CSS3 draft. It is now postponed to CSS4.

The pointer-events property has been supported by all modern browsers for some time now.

The pointer-events property is important to modern web applications.

It controls how HTML elements respond to mouse/touch/hover/click/tap events including hover/active states, and whether a cursor is visible.


Vendor Extensions

Why is this shown as a warning?

The W3C CSS Validator checks for CSS2 and CSS3 properties.

Some browser vendors have added prefixes to experiment with new (or nonstandard) CSS properties.

Browser vendors are working to stop using prefixes for experimental features.

Until then, some extensions will have to be used to make modern CSS work in all browsers.

Below is a list of the most common vendor extentions:

BrowserExtention
-webkit-Chrome, Safari, Opera
-moz-Firefox
-o-Old Opera versions
-ms-Microsoft Edge and Internet Explorer