Code Quality in CSS
One monumental principle of computer engineering is that software should be maintenance. It means that it shouldn't be hard to read, write, and edit existing software. This is easier to say than...
Typical browser caches all CSS and JS files to avoid unneeded download. In WordPress, this has a big effect on your changes to style.css file. These changes will not be immediately visible to old visitors.
Add the following code to your functions.php. It appends version number to the URL (in query string). Changing the version number forces a browser to re-download style.css.
function my_wp_default_styles_scripts($styles) {
$my_theme = wp_get_theme();
$styles->default_version = $my_theme->get( 'Version' );
}
add_action("wp_default_styles", "my_wp_default_styles_scripts");
add_action("wp_default_scripts", "my_wp_default_styles_scripts");
It’s a simple fix, but it’s not well documented in WordPress.