在看css实战手册，里面说任何html元素都有盒模型。我直接在<body>内建立一个<span>，设置margin、padding都为100px，为什么只有左右margin、padding为100px，而上下的margin和padding没有显示出来？
<!DOCTYPE html>
<html>
<head>
<title></title>
<style type="text/css">
span{
margin: 100px;
padding:100px;
}
</style>
</head>
<body>
<span>hahssssssssss</span>
</body>
</html>span元素默认display为inline，inline元素不显示上下的margin、padding
In an inline formatting context, boxes are laid out horizontally, one after the other, beginning at the top of a containing block. Horizontal margins, borders, and padding are respected between these boxes.