What is the order of precedence for CSS?

There are several rules ( applied in this order ) :

1. inline css ( html style attribute ) overrides css rules in style tag and css file
2. a more specific selector takes precedence over a less specific one
3. rules that appear later in the code override earlier rules if both have the same specificity.
4. A css rule with !important always takes precedence.

In your case its rule 3 that applies.

Specificity for single selectors from highest to lowest:

• ids (example: #main selects <div id="main">)
• classes (ex.: .myclass), attribute selectors (ex.: [href=^https:]) and pseudo-classes (ex.: :hover)
• elements (ex.: div) and pseudo-elements (ex.: ::before)

To compare the specificity of two combined selectors, compare the number of occurences of single selectors of each of the specificity groups above.

Example: compare #nav ul li a:hover to #nav ul li.active a::after

• count the number of id selectors: there is one for each (#nav)
• count the number of class selectors: there is one for each (:hover and .active)
• count the number of element selectors: there are 3 (ul li a) for the first and 4 for the second (ul li a ::after), thus the second combined selector is more specific.

A good article about css selector specificity.