HTML

Span
span元素的居中（需要设置span的display属性为block或者inline-block：

text-align: center;
line-height: 40px;//该高度为span的高度

Web

form-data对比 x-www-form-urlencoded

These are different Form content types defined by W3C. If you want to send simple text/ ASCII data, then x-www-form-urlencoded will work. This is the default.

But if you have to send non-ASCII text or large binary data, the form-data is for that.

You can use Raw if you want to send plain text or JSON or any other kind of string. Like the name suggests, Postman sends your raw string data as it is without modifications. The type of data that you are sending can be set by using the content-type header from the drop down.

Binary can be used when you want to attach non-textual data to the request, e.g. a video/audio file, images, or any other binary data file.

Refer to this link for further reading:Forms in HTML documents