How to center three divs horizontally within a parent div? [duplicate]

Question

I know this question has been frequently asked but I can never seem to get it to work. Can you tell me what's wrong?

I have three divs within a #container div, which I want to centre side by side. The #container is 1000px wide (I want to keep it that way). Here is my code:

#container {
  margin-top: 500px;
  position: absolute;
  width: 1000px;
}
.related-article {
  background-color: #D6A400;
  display: inline-block;
  width: 230px;
  height: 300px;
  border-radius: 30px;
  margin-bottom: 0px;
}
.related-article > img {
  width: 200px;
  height: 150px;
  border-radius: 15px;
  margin-top: 15px;
}
.related-article > h3 {
  font-size: 15px;
  width: 180px;
  text-align: justify;
  margin-left: auto;
  margin-right: auto;
  color: #f1f1f1;
  font-family: Abel, serif;
  margin-bottom: none;
}
a {
  text-decoration: none;
}
#right {
  float: right;
}
#left {
  float: left;
}
#center {
  margin-left: 385px;
  margin-right: 385px;
}

<div id="container">
  <h2>Here's what you'll do!</h2>
  <div id="left">
    <a href="#" class="related-article first" align="middle">
      <img src="download.jpeg" alt="T-rex">
      <h3>Constructing amazing fossils you never even dreamed of</h3>
    </a>
  </div>
  <div id="center">
    <a href="#" class="related-article second" align="middle">
      <img src="fossil-fish-10-lg.jpg" alt="Fish">
      <h3>Studying ancient marine biology</h3>
    </a>
  </div>
  <div id="right">
    <a href="#" class="related-article third" align="middle">
      <img src="fossil.turtle2.jpg" alt="Turtle">
      <h3>Uncovering the world's greatest mysteries</h3>
    </a>
  </div>
</div>

All help would be gladly appreciated.

Answer 1

You can do that quite simple using flexbox:

#container {
/*     margin-top: 500px; */
  width: 1000px;
  margin: 0 auto;
}
.related-article {
  background-color: #D6A400;
  display: inline-block;
  border-radius: 30px;
  margin-bottom: 0px;
}
.related-article > img {
    width: 200px;
    height: 150px;
    border-radius: 15px;
    margin-top: 15px;
}
.related-article > h3 {
  font-size: 15px;
  width: 180px;
  text-align: justify;
  margin-left: auto;
  margin-right: auto;
  color: #f1f1f1;
  font-family: Abel, serif;
  margin-bottom: none;
}
a {
    text-decoration: none;
}

}
#container {
    width: 1000px;
}

.related-article {
  background-color: #D6A400;
  display: inline-block;
  width: 230px;
  height: 300px;
  border-radius: 30px;
  margin-bottom: 0px;
}
.related-article > img {
    width: 200px;
    height: 150px;
    border-radius: 15px;
    margin-top: 15px;
}
.related-article > h3 {
  font-size: 15px;
  width: 180px;
  text-align: justify;
  margin-left: auto;
  margin-right: auto;
  color: #f1f1f1;
  font-family: Abel, serif;
  margin-bottom: none;
}
a {
    text-decoration: none;
}
.box {
  margin-right: 10px;
    width: 230px;
  height: 300px;
  }

.flex-container {
  display: flex;
  align-items: center;
  justify-content: center;
}

<div id="container">
        <h2>Here's what you'll do!</h2>
        <div class="flex-container">
        <div id="left" class="box">
          <a href="#" class="related-article first" align="middle">
            <img src="download.jpeg" alt="T-rex">
            <h3>Constructing amazing fossils you never even dreamed of</h3>
          </a>
          </div>
          <div id="center"  class="box">
          <a href="#" class="related-article second" align="middle">
            <img src="fossil-fish-10-lg.jpg" alt="Fish">
            <h3>Studying ancient marine biology</h3>
          </a>
          </div>
          <div id="right"  class="box">
          <a href="#" class="related-article third" align="middle">
            <img src="fossil.turtle2.jpg" alt="Turtle">
            <h3>Uncovering the world's greatest mysteries</h3>
          </a>
          </div>
          </div>
        </div>

Answer 2

A solution using display: flex. Read more about flexbox here

1. Apply display: flex to the container
2. Add flex: 1 to all the child's which are to be centered horizontally.

h2 {
  margin-top: 500px;
}
#container {
  position: absolute;
  width: 1000px;
  display: flex;
  text-align: center;
}
#container div {
  flex: 1;
}
.related-article {
  background-color: #D6A400;
  display: inline-block;
  width: 230px;
  height: 300px;
  border-radius: 30px;
  margin-bottom: 0px;
}
.related-article > img {
  width: 200px;
  height: 150px;
  border-radius: 15px;
  margin-top: 15px;
}
.related-article > h3 {
  font-size: 15px;
  width: 180px;
  text-align: justify;
  margin-left: auto;
  margin-right: auto;
  color: #f1f1f1;
  font-family: Abel, serif;
  margin-bottom: none;
}
a {
  text-decoration: none;
}

<h2>Here's what you'll do!</h2>
<div id="container">
  <div id="left">
    <a href="#" class="related-article first" align="middle">
      <img src="download.jpeg" alt="T-rex">
      <h3>Constructing amazing fossils you never even dreamed of</h3>
    </a>
  </div>
  <div id="center">
    <a href="#" class="related-article second" align="middle">
      <img src="fossil-fish-10-lg.jpg" alt="Fish">
      <h3>Studying ancient marine biology</h3>
    </a>
  </div>
  <div id="right">
    <a href="#" class="related-article third" align="middle">
      <img src="fossil.turtle2.jpg" alt="Turtle">
      <h3>Uncovering the world's greatest mysteries</h3>
    </a>
  </div>
</div>