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                <!DOCTYPE html>
/* Style cho phần tử có id="myHeader" */
#myHeader {
  background-color: lightblue;
  color: black;
  padding: 40px;
  text-align: center;

/* Style cho tất phần tử có class="city" */
.city {
  background-color: tomato;
  color: white;
  padding: 10px;

<h2>Difference Between Class and ID</h2>
<p>An HTML page can only have one unique id applied to one specific element, while a class name can be applied to multiple elements.</p>

<!-- Một phần tử duy nhất -->
<h1 id="myHeader">My Cities</h1>

<!-- Nhiều phần tử giống nhau -->
<h2 class="city">London</h2>
<p>London is the capital of England.</p>

<h2 class="city">Paris</h2>
<p>Paris is the capital of France.</p>

<h2 class="city">Tokyo</h2>
<p>Tokyo is the capital of Japan.</p>