要使元素在后面有换行符，为它赋值:

显示:块;

块级元素之后的非浮动元素将在下一行出现。许多元素，如<p>和<div>已经是块级元素，所以您可以只使用它们。

But while this is good to know, this really depends more on the context of your content. In your example, you would not want to use CSS to force a line break. The <br /> is appropriate because semantically the p tag is the the most appropriate for the text you are displaying. More markup just to hang CSS off it is unnecessary. Technically it's not exactly a paragraph, but there is no <greeting> tag, so use what you have. Describing your content well with HTMl is way more important - after you have that then figure out how to make it look pretty.

<pre>标签呢?

来源:http://www.w3schools.com/tags/tag_pre.asp

我喜欢非常简单的解决方案，这里还有一个:

<p>hello <span>How are you</span></p>

和CSS:

p {
  display: flex;
  flex-direction: column;
}

代码可以是:

<div class="text-class"><span>hello</span><span>How are you</span></div>

CSS将是:

.text-class {
  display: flex;
  justify-content: flex-start;
  flex-direction: column;
  align-items: center;
}

在我的例子中，我需要一个输入按钮前面有一个换行符。 我应用如下样式的按钮，它工作:

clear:both;

下面是一个糟糕问题的糟糕解决方案，但它确实符合概要:

p {
    width : 12ex;
}

p:before {
    content: ".";
    float: right;
    padding-left: 6ex;
    visibility: hidden;
}