source/misc/embedded_libs/fmt-8.1.1/doc/bootstrap/mixins/center-block.less
browsing at commit = 607bd2a1a1f219b1c9acd67a3f404410b6c4ed6c
// Center-align a block level element
.center-block() {
display: block;
margin-left: auto;
margin-right: auto;
}