problem

HTML

<div id="container">
    <div id="DivB">Just another text.</div><div id="DivA">Lots and lots of text. Lots and lots of text.Lots and lots of text. Lots and lots of text. Lots and lots of text. Lots and lots of text. Lots and lots of text. Lots and lots of text. Lots and lots of text.</div>
</div>

CSS

#container {
    display: table;
}
#container > div {
  display: inline-block;
  vertical-align: middle;
}
#DivA {
    background: #ccc;
    width: 25%;
}
#DivB {
    background: #000;
    color: #FFF;
    vertical-align:middle;
    width: 75%;
}