html:
<img src="paris.jpg" alt="Paris" class="center">
css:
<style>
.center {
display: block;
margin-left: auto;
margin-right: auto;
width: 50%;
}
<style><div class="verticalhorizontal">
<img src="image.jpg" alt="centered image" />
</div>
<style>
.verticalhorizontal {
display: table-cell;
height: 300px;
text-align: center;
width: 300px;
vertical-align: middle;
}
</style>.center {
display: block;
margin-left: auto;
margin-right: auto;
width: 50%;
}<!-- HTML here not CSS! -->
<!DOCTYPE html>
<head><!-- Title goes here --></head>
<body>
<center><!-- Center's anythings -->
<img src""><!-- Put image name (e.g example.jpeg) -->
</center>
</body>
</html>