Why can't I set the width and height of a span?

Why can't I set the width and height of a span?

Why cannot I set the width and height of a span:
Suggestion: writing code as much as possible can effectively improve learning efficiency and depth.
Many users may encounter this problem when learning the div + css layout. the height and width of the span cannot be set using the CSS code, but the CSS Code cannot take effect even if there is no error. For example

<! DOCTYPE html>  
In the preceding code, the height and width of the specified span element cannot take effect. This is because the width and height cannot be set for the inline element. To set the width and height, you must first convert the inline element to a block-level element, you can set the display attribute value of an inline element to block. The CSS code is modified as follows:
 
Width: 200px; height: 200px; display: block; border: 1px solid red;
 
The original address is: http://www.softwhy.com/forum.php? Mod = viewthread & tid = 4708.
 
For more information, see: http://www.softwhy.com/divcss/