Q1. What is universal selector?

* selects all elements on the page.

Q2. Common use of universal selector?

CSS resets: * { margin: 0; padding: 0; box-sizing: border-box; }

Q3. What is specificity of universal selector?

Universal selector has 0 specificity, easily overridden by any other selector.

Q4. Potential downside of universal selector?

Can affect performance if overused, and may unintentionally style form elements negatively.

Q5. Can universal selector be combined?

Yes, e.g., div * selects all descendants of div.