CSS is rarely the major bottleneck in application performance. Of course there may be exceptions involving huge systems, or extremely poorly written CSS rules, or use of CSS properties with known performance implications.
Human CSS classes offer improved performance because the dozens or hundreds of CSS files often seen in poorly-engineered applications are much smaller (or not needed at all). This reduces both download and processing time.
We do not use or support floats, and neither should you.
We neither need nor use !important, and we recommend you do not either.
Some element-specific styling can obviously not be handled with micro-attributes,
background-image for example.
If a page has only one or two such cases, we suggest inlining the rule with the style attribute.
We are not religious zealots, and this can be a better approach than creating a separate CSS file
and defining an additional class merely in order to target the element.
The following CSS features require more complex properties which are not well-suited to the micro-attribute approach, and therefore are not (currently) supported:
- Animations or more complex transitions
- Box shadows and text shadows
- Properties involving URLs, such as
background-image - Pseudo-classes
- Pseudo-elements
Some of thse might be able to be supported when browser support for the attr() function is available.