vertical alignment

HTML

<div class="root" id="top"><!--
    --><button class="inline">button</button><!--
    --><div class="inline parent"><div class="child">relative</div></div><!--
    --><button class="inline">button</button><!--
--></div>

   <div class="root" id="bottom"><!--
    --><button class="inline">button</button><!--
    --><div class="inline parent"><div class="child">absolute</div></div><!--
    --><button class="inline">button</button><!--
--></div>

CSS

.root {
    margin: 25px;
    padding: 25px;
}

.inline {
    width: 85px;
    height: 25px;
    position: relative;
}

.parent {
    background-color: #ccc;
    border-color: #ccc;
    display: inline-block;
}

#top .child {
    position: relative;
}

#bottom .child {
    position: absolute;
}

.inline {
    border-style: solid;
    text-align: center;

    padding-left: 6px;
    padding-right: 6px;
    padding-bottom: 1px;
}

.inline {
    box-sizing: border-box;
    font-family: Arial;
    padding-top: 1px;
}