Center Div inside another (100% width) div

Question

Quite a \"simple\" problem here and not sure why it\'s being so complicated.

1. Have a 100% (width) sized div.
2. Have another div positioned in the middle

Answer 1

.outerdiv {
    margin-left: auto;
    margin-right: auto;
    display: table;
}

Doesn't work in internet explorer 7... but who cares ?