How to center things – display:block/inline-block

Block elements should always be centered using

.block {
    margin-left: auto;
    margin-right: auto;
    width: 600px;
}

as stated by the w3c: http://www.w3.org/Style/Examples/007/center.en.html#block

text-align: center;

is well-named: use it to center texts.

Update

You can also use display: flex now:

.parent {
    display: flex;
    justify-content: center;
}
.block {
    width: 200px;
}