Nav bar border issue using css

In my case I am having a nav bar(two tabs) with green border. Below this there is a container with green border. For active tab border-bottom should be white and another tab should be green. So I changed border-bottom:1px solid #fff for active tab alone. This case is working fine is large and medium device. But in small device green line is still displaying under active tab which is the border of the container present under the nav.