Question

How to make div horizontally and vertically centered without scripting?
Only on CSS and HTML5?

<div id="center"></div>

#center{width:500px; height:300px;}

Answer 1

For fixed size :

#center{
    width:500px;
    height:300px;
    position:absolute;
    top:50%;
    left:50%;
    margin:-150px 0 0 -250px;
}

If you want to resize your div with the screen you can use this technique which works for div too.