What causes a vertical position change in buttons with content floated left or right? Take this example http://jsfiddle.net/8ff6dhou/
<button>aaa</button>
<button><div style="float:left">bbb</div></button>
<button><div style="float:right">ccc</div></button>
<button>ddd</button>
Why are the 4 buttons not at the same vertical position? Is there a way to resolve this issue?