I'm not sure what lines you are referring to, Firefox normally draws a border around the active tab. Note that Firefox may show a userContext line for containers.

You can use the Browser Toolbox to see what CSS rules causes those lines. Note that you need to enable the toolbox to be able to use it.

• https://developer.mozilla.org/en-US/docs/Tools/Browser_Toolbox

See also the Firefox CSS subreddit forum.

• https://www.reddit.com/r/FirefoxCSS/

Thanks Corel , sorry for not being clear enough. As of Firefox version 102 the developers decided to add to the active tab outlining , 2 horizontal lines (as you can see in the image I attached). Since I kept the older angled tab shape , it now looks quite absurd. I tried to play with my userchrome.css , but to no avail. Hope I now made my issue clearer. Thanks.

What is the current CSS code for the selected tab ?

I assume that you style .tab-background to get the rounded tabs, you may have to look at .tab-context-line as well. See .tab-background:

• https://searchfox.org/mozilla-release/source/browser/themes/shared/tabs.css

See .tab-context-line:

• https://searchfox.org/mozilla-release/source/browser/components/contextualidentity/content/usercontext.css

Thanks a lot Corel , I went over the stuff you sent me but that did not solve the issue. I almost gave up , so as a last resort , I dug into my large css code and finally came up with the solution which I must say , was quite simple once you know "how to address the item"(that was initially my problem). I must say that each Firefox upgrade I find myself rather anxious , just to find out that those who are responsible for the upgrade sometimes play with trifles instead of addressing major issues. What was so important/urgent/necessary to mess with the tab shape , I wonder. It makes me mad. Anyhow , I thank you Corel for always being there to help , thank you indeed. look4.

Can you tell us what code this was about ?

The solution was :

tab[selected="true"] .tab-stack { color:transparent !important; }

look4