QR Code using CSS Grid and Flexbox

Replace <div class="container"> with the main tag to make the page /content accessible. click here for more on web-accessibility and semantic html

Give the alt attribute in the img a value. The value of the alt attribute is the description of the image. For decorative images like icons, there is no need to give it an alt value, for more on alt attribute Click here.

There is no need to give .cn a height value . For a responsive content, replace the width in .cn and the img with max-width.

To center .cn on the page using grid, add min-height:100vh; display: grid place-items: center to the body. For centering using grid Click here

body{
min-height: 100vh;
display: grid;
place-items: center;
}

Use relative units like rem or em as unit for the padding, margin, width values and preferably rem for the font-size values, instead of using px which is an absolute unit. For more on CSS units Click here

Give h1 and p the same font-size of 15px which is 0.9375rem, text-align: center, the same margin-left, margin-right and margin-top values. Give p a margin bottom value.

Hope am helpful.

Well done for completing this challenge. HAPPY CODING