zblog/themes/zero/static/style.css

* {
  box-sizing: border-box; 
}

.entries {
  list-style-type: none;
  display: flex;
  flex-flow: row wrap;
  justify-content: center;
}

.entries > li {
  width: 33%;
  min-width: 400px;
  padding: 1em;
}