CSS content contains duplicate CSS properties
This means that the URL in question is a CSS file that contains one or more duplicate CSS properties.
Why is this important?
Duplicate properties are typically the result of a coding error, and the duplication is completely redundant in cases where repeat the same value. In cases where the values conflict, then the value which ends up getting rendered may not be as intended.
What does the Hint check?
This Hint will trigger for any internal or external CSS URL which contains duplicate CSS properties
Examples that trigger this Hint:
The Hint would trigger for any style sheet that contains duplicate CSS properties. Either properties with the same value that are immediately adjacent:
Or duplicate properties that are separated by another property:
How do you resolve this issue?
It is recommended to remove unintentional duplicate properties because they can be safely removed to save bytes.
It is worth nothing that there are circumstances where this is intentional, and put in place to deal with varying levels of browser support. For example, some browsers support RGBA colour while others do not, so it's quite common to include both options.