How to set a div to be centered horizontally and vertically? _html/css_WEB-ITnose

How to set a div to be centered horizontally and vertically?
Note that it is not the content of the div that is centered horizontally and vertically, but the div itself.
What I found online is that the content of the div is centered horizontally and vertically.
If you want to center it horizontally, margin:0 auto; will work.
I tried many things vertically but nothing worked.

Reply to discussion (solution)

http://www.cnblogs.com/yjzhu/archive/2012/11/19/2773209.html
http:/ /www.w3cplus.com/css/vertically-center-content-with-css
I have written two articles, I hope it will be helpful to LZ.

http://www.cnblogs.com/yjzhu/archive/2012/11/19/2773209.html
http://www.w3cplus.com/css/vertically-center-content- with-css
I have posted two articles, I hope it will be helpful to LZ.
Thanks, done