While true, you'll need a whole lot of slow selectors before your CSS will be the speed bottleneck. It's more noticeable if you use jQuery/other complex javasc

While true, you'll need a whole lot of slow selectors before your CSS will be the speed bottleneck. It's more noticeable if you use jQuery/other complex javascript DOM selectors, but the solution there is caching or using .find(). JS dom querying is also going native with QuerySelectorAll, so in time it will become less of an issue here, too. Write your CSS for yourself, make it maintainable and easy to read. Let browsers figure out how to make it fast.