Version 3.1.0 of the Hello Theme introduces new features and makes the already light theme even faster. However, some of these changes involve removing or replacing HTML elements. These modifications can cause sites with custom CSS to produce unexpected results.
The Issue
After upgrading the Hello Theme to version 3.1.0, custom CSS code that uses element selectors no longer works. This includes Custom CSS that changes theme styles or uses JS to query elements in order to add functionality.
Possible Cause
The Hello Theme 3.1.0 changes a number of HTML elements. These elements may be part of the site’s custom CSS code.
Solution
Update the element selectors used in the custom CSS code so they are compatible with Hello Theme 3.1.0. For details about the specific changes made to the Hello Theme, see the Developer notes.