media quary to control div width

A div and its children inputs need to have width:100% when screen is less than 600px wide. Why the code below fails to do that?
I need to have the dives side by side when screen is above 600px and below each other 100% width on smaller scr…

Alternative to margin 0 auto with CSS grid?

Is there a way to achieve the same but with a CSS grid?
const fullWidth = {
width: "100%"

const maxWidth = {
maxWidth: "1280px",
margin: "0 auto"

export default function Header({ title }) {

Tab closes when opening nested tab

Below example has a tab called London with another tab in it called Paris. How can I open Paris without the London tab closing?
The example is directly from W3SCHOOL but modified a bit to fit my use case.

<!DOCTYPE html>

CSS hover effect does not work and I find it lost

Below code doesn’t work in any other browser.I’d like to use a hover effect to change the property of popup ,but it doesn’t work.And I can’t find this style in google chrome developer tools.
.footer-about-yqsl ul.footer-social .social-wec…