how to align elements horizontally in css

.row {
  width: 100%;
  display: flex;
  flex-direction: row;
  justify-content: center;
}
.block {
  width: 100px;
}

#inner {
  display: table;
  margin: 0 auto;
  border: 1px solid black;
}

#outer {
  border: 1px solid red;
  width:100%
}

<-- Html -->

<div id="outer">
  <div id="inner">Foo foo</div>
</div>

<div class="row">
  <div class="block">Lorem</div>
  <div class="block">Ipsum</div>
  <div class="block">Dolor</div>
</div>