css how to make elements in div align vertically code example

Example 1: centering horizontally

div.center{display:block;margin:auto;width:50%;}
p.center{text-align:center;}

Example 2: vertical align into div

#parent {position: relative;}

#child {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    width: 50%;
    height: 30%;
    margin: auto;
}