Vertical middle alignment of text not working

[mrtukker]

I want to vertically middle align text in a div that has height in percentage. The code i am using is this.CSS-\[code\].div{ position: fixed; left: 0px; border-radius: 10px; height: 6%; width: 20%; transform: translate(-10px,0px); -ms-transform: translate(-10px,0px); -webkit-transform: translate(-10px,0px); -o-transform: translate(-10px,0px); -moz-transform: translate(-10px,0px); z-index: 10}.div span { text-align: center; font: 20px/100% Arial, Helvetica, sans-serif; text-decoration: none; color: #fff; display: block; vertical-align: middle;}\[/code\]HTML-\[code\]<div class="div"><span>This is some text.</span></div>\[/code\]This isnt working. Please help.