使用overflow-wrap: break-word;如:

.yourelement{
  overflow-wrap: break-word;
}

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.

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;
}

CSS中的“\a”命令生成一个回车。这是CSS，不是HTML，所以它应该更接近你想要的:没有额外的标记。

在一个blockquote中，下面的例子同时显示标题和源链接，并用回车符("\a")分隔两者:

blockquote[title][cite]:after {
  content:attr(title)"\a"attr(cite)
}

例如，您可以添加大量的填充和强制文本拆分到新行

p {
  padding-right: 50%;
}

对我来说，在响应式设计的情况下工作得很好，只有在一定的宽度范围内，文本才需要被分割。

<pre>标签呢?

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