Active tab style

You add custom style in the theme's style.css file, or, if you're using a child theme, edit the same file in the child theme folder. Do not change tabs-left in the shortcode plugin folder. If your browser can inspect a page code, check the existing style parameters then substitute them in your style.css. Keep in mind two things: 1. Some theme styles use more specific class names (nested classes chain), so they have a priority over the general one, and you have to use the same specific nested style class chain to get power over the theme's ones. In your case you have to work not with .<span style="line-height: 1.5;">tabs-left</span> but with <span style="line-height: 1.5;">.content .tabs-left </span> .tabs-left .nav > li > a etc. 2. In some cases in order to overwrite the theme's code you have to enforce your's with !important, although do not use it unless you're sure that, say <em style="line-height: 1.5;"><span style="line-height: 1.5;"> .tabs-left </span><span style="line-height: 1.5;">is unique to tabs only. If you enforce your style I'd suggest to check how it changes the mobile style as well.</span> In your case the enforced style will be .tabs-left .nav > li > a {padding: 17px 24px !important} I hope it makes sense for you.