http://codepen.io/ayoungh/pen/ABJKu

HTML
<textarea id="comment_text" class="ui-autocomplete-input" cols="30" rows="10" name="comment[text]">Texto</textarea>

CSS

<style type="text/css"> <!--body {background: #F0F0F0; } h2 {margin-left: 55px; } textarea { margin-top: 10px; margin-left: 50px; width: 500px; height: 100px; -moz-border-bottom-colors: none; -moz-border-left-colors: none; -moz-border-right-colors: none; -moz-border-top-colors: none; background: none repeat scroll 0 0 rgba(0, 0, 0, 0.07); border-color: -moz-use-text-color #FFFFFF #FFFFFF -moz-use-text-color; border-image: none; border-radius: 6px 6px 6px 6px; border-style: none solid solid none; border-width: medium 1px 1px medium; box-shadow: 0 1px 2px rgba(0, 0, 0, 0.12) inset; color: #555555; font-family: "Edwardian Script ITC"; font-size: 1em; line-height: 1.4em; padding: 5px 8px; transition: background-color 0.2s ease 0s; } textarea:focus { background: none repeat scroll 0 0 #FFFFFF; outline-width: 0; } --></style>