Это самый короткий и простой способ.Вы устанавливаете фиксированную ширину и задаете для нее автоматическое поле, чтобы оно было отцентрировано.
.container {
width: 300px;
margin: 0 auto;
}
<div class="container">
<p>
Lorem Ipsum is simply dummy text<br> Lorem Ipsum has been the industry's <br> when an unknown printer took a galley <br> It has survived not only five centuries,<br> remaining essentially unchanged. It was<br> of Letraset sheets containing Lorem Ipsum<br> publishing software like Aldus PageMaker.</p>
</div>
Если ваш макет более сложный, вы можете использовать flex.Например:
.container {
width: 100%;
display: flex;
align-items: center;
justify-content: center;
}
.content{
flex-basis: 300px;
flex-grow: 0;
flex-shrink: 0;
}
<div class="container">
<div class="content">
<p>
Lorem Ipsum is simply dummy text<br> Lorem Ipsum has been the industry's <br> when an unknown printer took a galley <br> It has survived not only five centuries,<br> remaining essentially unchanged. It was<br> of Letraset sheets containing Lorem Ipsum<br> publishing software like Aldus PageMaker.</p>
</div>
</div>