Parts of CSS3 are already faster to implement "by hand" in javascript rather than using the browser's "native" implementation.
HTML/CSS was designed for requirements that don't apply to many modern websites. I would not be surprised if it were possible to implement a rendering engine that performed better for relevant use cases, e.g. perhaps assuming a grid as a first-class part of the layout.
HTML/CSS was designed for requirements that don't apply to many modern websites. I would not be surprised if it were possible to implement a rendering engine that performed better for relevant use cases, e.g. perhaps assuming a grid as a first-class part of the layout.