container to center of screen code example

Example 1: how to put container in center of page

#container
{
    width: 400px;
    margin-left: auto;
    margin-right: auto;
}

Example 2: css position element in the middle of a header

P.blocktext {
    margin-left: auto;
    margin-right: auto;
    width: 200px;/*usually works best with a fixed width*/
}