In the olden days of HTML development, in the late 90ies, we only had inline styles. Centring an element was done using the <center> property. That approach isn’t very elegant anymore in modern CSS 
Today we can use something like this:
#your-id .your-class {
display: block;
margin-left: auto;
margin-right: auto;
}It’s slightly more complicated than a single tag, but also opens up more options to tweak top and bottom margins at the same time.