Is the CSS star selector considered harmful (and why)?

Question

Does the star selector in CSS affect page rendering performance?

Are there any caveats using it?

* {   margin:0;   padding:0; } 

Answer 1

When it comes to performance, Steve Souders is the man:

• Performance Impact of CSS Selectors
• Simplifying CSS Selectors

Shameless quote from one of the reports:

The key to optimizing CSS selectors is to focus on the rightmost selector, also called the key selector (coincidence?). Here’s a much more expensive selector: A.class0007 * {}. Although this selector might look simpler, it’s more expensive for the browser to match. Because the browser moves right to left, it starts by checking all the elements that match the key selector, “*“. This means the browser must try to match this selector against all elements in the page.

[bold emphasis mine]