Provides a way to blend background images, colors, and gradients together.

Add support for scrollbar styling, similar to the earlier properties supported in Internet Explorer (i.e. scrollbar-base-color, etc)

https://drafts.csswg.org/selectors/#relational

The relational pseudo-class, ‘:has()#’, is a functional pseudo-class taking a relative selector list as an argument. It represents an element if any of the relative selectors, when absolutized and evaluated with the element as the :scope elements, would match at least one element.

Conic gradients [1] are useful for a number of effects on the Web that cannot be emulated in any other way (see [2]). They can be implemented in many graphics libraries today (e.g. Cairo) via mesh gradients. Please implement them.

[1]: http://www.w3.org/TR/css4-images/#conic-gradients
[2]: http://leaverou.github.io/conic-gradient

Please implement the :scope pseudo-class to refer to the context in querySelector(All). You’re the last browser remaining [1]

[1]: https://developer.mozilla.org/en-US/docs/Web/CSS/%3Ascope

Now that both Firefox 39+ and Safari 9 supports it in addition to being in development in Chrome, updating the Scroll Snap Points implementation to match the current spec is crucial. The current implementation from the IE 10 days is outdated and incompatible with the changes made since then.

Why hasn't there been any talk regarding this, and why hasn't it been done already?

Spec: https://drafts.csswg.org/css-snappoints/

Allows attr() to be used in any CSS rule (not just generated content), any CSS property (not just content) and for various data types.

Spec: http://www.w3.org/TR/css3-values/#attr-notation

This will revolutionize what we can do with CSS and enable a kind of decoupling between content and styling that has never been possible before.

This declaration is used to preserve pixels when scaling up images (e.g. pixel art). IE provides this functionality via -ms-interpolation-mode: nearest-neighbor. The other browser engines also provide this functionality (see here: http://www.simevidas.com/2015/05/10/Blowing-up-pixel-art-on-the-Web.html).

Introduces logical properties and values that provide the author with the ability to control layout through logical, rather than physical, direction and dimension mappings.

Please just axe IE and don't rebrand with the Spartan project. You're literally the worst browser in every conceivable test http://html5test.com http://css3test.com and yet you make fun of people who critique you instead of dumping resources into fixing your garbage browser. https://www.youtube.com/watch?v=lD9FAOPBiDk

So happy Chrome is bashing you nowadays. You deserve it.

Support CSS clip-path shapes, url(), etc.

http://www.w3.org/TR/css-masking-1/#the-clip-path
http://caniuse.com/#search=clip-path

http://dev.w3.org/csswg/css-images-3/#image-set-notation

Supported by Firefox and Chrome and gives the developer more control over CSS cascading. This would be helpful when when writing components that get inserted in other environments.

Preferably both property: initial and all: initial would be supported.

CSS3 tab-size is supported in all other browsers, and defines how many spaces the tab character should consist of.

http://dev.w3.org/csswg/css-text/#propdef-tab-size

Update the IE implementation of Regions to match the current spec and interoperate with the Safari implementation

Define arbitrary shapes inside and around which inline content can flow.

http://dev.w3.org/csswg/css-shapes/

CSS properties for aligning boxes within their container. Allows for true vertical centering among other features.

http://dev.w3.org/csswg/css3-align/

Adds a will-change CSS property, that can be used to signal that a particular property is likely to be changed in the future, or that an element's content is likely to change.

Proposal: http://tabatkins.github.io/specs/css-will-change/

Extends the CSS sizing properties with keywords that represent content-based "intrinsic" sizes and context-based "extrinsic" sizes, allowing CSS to more easily describe boxes that fit their content or fit into a particular layout context.

http://dev.w3.org/csswg/css3-sizing/