Flex-box example.

HTML

<body>
    <div class="horizontal">
        <img src="https://lorempixel.com/400/200/" />
        <img src="https://lorempixel.com/500/200/" />
        <img src="https://lorempixel.com/600/200/" />
        <img src="https://lorempixel.com/300/200/" />
        
    </div>
</body>

CSS

.flex-box{
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
}

img {
    margin: 5px;
}
.horizontal{
  display: inline-block;
}