Font vertical centering in css_html/css_WEB-ITnose

defined in css:

body{                                     
text-align: center;
vertical-align:middle;
font: 16px Arial, Song Dynasty;

}

But the font cannot be vertically centered, why?

Reply to discussion (solution)

But the font cannot be vertically centered, why?

re:

If you don’t give a height, how can it be vertically centered? Like I asked you to calculate the sum of n-n, do you know what n-n stands for?

Centering a single line of text line-height