Question 1

Should I use rem or px?

Accepted Answer

Use rem for type and type-related spacing so the interface scales when a user raises their browser font size. Use px where scaling would be wrong, such as border widths.

Question 2

What's the difference between em and rem?

Accepted Answer

rem is always relative to the root font size; em is relative to the nearest parent. Nested ems multiply together and quickly become unpredictable.

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