как на сайте http://murclub.ru/

<a class="btn" href="javascript:document.logform.submit()">Вой ти</a>

<link href="/css/design.css?1899" rel="stylesheet" type="text/css">

a.btn{text-align:center;width:250px;display:inline;margin-left:65px;}
a.btn{background:url(../img/btn.gif);background-position:bottom;background-repeat:repeat-x;height:31px;line-height:31px;width:auto;border:#09F solid 1px;font-weight:700;text-align:center;vertical-align:middle;color:#333;margin-right:10px;margin-bottom:10px;background-color:#FFF;float:left;padding:10px 30px;}
a.btn:hover{border:#333 solid 1px;}