Vertical align text in block element

You can also try

a {
  height:100px;
  line-height:100px;
}

According to the CSS Flexible Box Layout Module, you can declare the a element as a flex container (see figure) and use align-items to vertically align text along the cross axis (which is perpendicular to the main axis).

All you need to do is:

display: flex;
align-items: center;

See this fiddle.