W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
* {
  box-sizing: border-box;
}

body {
  font-family: Arial, Helvetica, sans-serif;
}

/* Float four columns side by side */
.column {
  float: left;
  width: 25%;
  padding: 0 10px;
}

/* Remove extra left and right margins, due to padding */
.row {margin: 0 -5px;}

/* Clear floats after the columns */
.row:after {
  content: "";
  display: table;
  clear: both;
}

/* Responsive columns */
@media screen and (max-width: 600px) {
  .column {
    width: 100%;
    display: block;
    margin-bottom: 20px;
  }
}

/* Style the counter cards */
.card {
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2);
  padding: 16px;
  text-align: center;
  background-color: #f1f1f1;
}
</style>
</head>
<body>

<h2>Responsive Column Cards</h2>
<p>Resize the browser window to see the effect.</p>

</body>
</html>

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<!DOCTYPE html><html><head><meta name="viewport" content="width=device-width, initial-scale=1"><style>* {  box-sizing: border-box;}​body {  font-family: Arial, Helvetica, sans-serif;}​/* Float four columns side by side */.column {  float: left;  width: 25%;  padding: 0 10px;}​/* Remove extra left and right margins, due to padding */.row {margin: 0 -5px;}​/* Clear floats after the columns */.row:after {  content: "";  display: table;  clear: both;}​/* Responsive columns */@media screen and (max-width: 600px) {  .column {    width: 100%;    display: block;    margin-bottom: 20px;  }}​/* Style the counter cards */.card {  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2);  padding: 16px;  text-align: center;  background-color: #f1f1f1;}</style>