You can attach classes to HTML elements by using class="your-class-here"
within the relevant element's opening tag.
CSS selectors require a period at the beginning like this: .blue-text { color: blue; }
, but that class declaration in the HTML doesn't use a period, like this: <h2 class="blue-text">CatPhotoApp<h2>
.
<style>
.red-text {
color: red;
}
</style>
<h2 class="red-text">CatPhotoApp</h2>
<p class="red-text">Kitty ipsum dolor sit amet, shed everywhere shed everywhere stretching attack your ankles chase the red dot, hairball run catnip eat the grass sniff.</p>