[Atomskun]

> so the usage of margin-top should always be avoided

Not really if you consider sibling layouts, e.g.: https://matthewjamestaylor.com/css-margin-top-vs-bottom

> owl selector: performance implications - it's fairly bad from a performance POV to use it.

Arguing about "CSS performance" is futile when the real cause of bloatedness is mostly JavaScript these days (also: http://alistapart.com/article/axiomatic-css-and-lobotomized-...).

The owl-selector can actually be quite elegant, but becomes a burden if you have lots of side-by-side blocks (which would always need to set their margin-top to 0).

[ry_ry]

I was suprised the degree to which selector performance is a negligible overhead in normal use these days.

Was browsing through the docs for some Vue+CSS library or another recently, and the author had done quite a lot of research into this, was interesting.

They were heavily using the square bracket html-attribute selector notation, although I'm not sure if it performs better now, or if modern processors are just that much faster.