The cascade
The cascade is how the browser decides which rule wins when several target the same element.
Definition
The cascade is how the browser decides which rule wins when several target the same element. It weighs where a rule comes from, how specific it is and the order it was written.
Use case
When a style refuses to apply, the cascade explains why. Check which rule is winning in your browser's developer tools.
Related terms
Documentation
CSS cascading and inheritance
The reference on how conflicting declarations are resolved.