Why does an inline element accept width and height when floated?

问题

Now I have a span element I give it width and height for example 500px I know it inline element so it doesn't accept width and height but why it applies when I float it??

span.first {
  width: 500px;
  height: 500px;
  border: 1px solid #000;
  float: right;
}

span.second {
  width: 500px;
  height: 500px;
  border: 1px solid #000;
}

<span class="first">with float</span>
<span class="second">without float</span>

https://codepen.io/kemozzz/pen/KvVrXj

回答1:

In accordance with CSS rules, when you apply float to an element, in most cases it becomes a block element. Elements that are inline and inline-block will compute to block.

From MDN:

回答2:

When you float an element, it automatically becomes display: block.

From the spec:

https://www.w3.org/TR/CSS22/visuren.html#dis-pos-flo

来源：https://stackoverflow.com/questions/45404969/why-does-an-inline-element-accept-width-and-height-when-floated