html center image

.center {
  display: block;
  margin-left: auto;
  margin-right: auto;
}

img {
  display: block;
  margin-left: auto;
  margin-right: auto;
}

.centerImg {
  display: block;
  margin: 0 auto;
}

  .center {
  display: block;
  
  margin-left: auto;
  margin-right: auto;
  
  width: 50%;
} 

.center {
  display: block;
  margin-left: auto;
  margin-right: auto;
  width: 50%;
}

<div style="text-align: center;">
  <img scr='img/example.jpg'>
</div>

.someclass {
  display: block;
  margin-left: auto;
  margin-right: auto;
}

/* html */
<h1>Centering with CSS</h1>

<h3>Text-Align Method</h3>
<div class="blue-square-container">
  <div class="blue-square"></div>
</div>

<h3>Margin Auto Method</h3>
<div class="yellow-square"></div>

<h3>Absolute Positioning Method</h3>
<div class="green-square"></div>

/* css */
h1,
h3 {
  text-align: center;
}

.blue-square-container {
  text-align: center;
}

.blue-square {
  background-color: #0074D9;
  width: 100px;
  height: 100px;
  display: inline-block;
}