グラデーションをサポートしていないブラウザーのバックアップとして、画像付きのグラデーション背景を使用します。画像の背景は自動的に並べて表示され、境界線の半径によって角が丸くなります。
デモhttp://jsfiddle.net/kevinPHPkevin/hSwJN/16/
#submit {
-moz-border-radius: 5px;
-webkit-border-radius: 5px;
border-radius:6px;
display: inline-block;
color: #000;
font-family:'Oswald';
font-size: 20px;
padding: 12px 24px;
border:none;
background:url('http://www.islandpoolnspa.com/More_info_button_background_rot_180.jpg');
background: rgb(76,76,76); /* Old browsers */
background: -moz-linear-gradient(top, rgba(76,76,76,1) 0%, rgba(89,89,89,1) 12%, rgba(71,71,71,1) 39%, rgba(44,44,44,1) 50%, rgba(0,0,0,1) 51%, rgba(17,17,17,1) 60%, rgba(28,28,28,1) 91%, rgba(19,19,19,1) 100%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,rgba(76,76,76,1)), color-stop(12%,rgba(89,89,89,1)), color-stop(39%,rgba(71,71,71,1)), color-stop(50%,rgba(44,44,44,1)), color-stop(51%,rgba(0,0,0,1)), color-stop(60%,rgba(17,17,17,1)), color-stop(91%,rgba(28,28,28,1)), color-stop(100%,rgba(19,19,19,1))); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top, rgba(76,76,76,1) 0%,rgba(89,89,89,1) 12%,rgba(71,71,71,1) 39%,rgba(44,44,44,1) 50%,rgba(0,0,0,1) 51%,rgba(17,17,17,1) 60%,rgba(28,28,28,1) 91%,rgba(19,19,19,1) 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(top, rgba(76,76,76,1) 0%,rgba(89,89,89,1) 12%,rgba(71,71,71,1) 39%,rgba(44,44,44,1) 50%,rgba(0,0,0,1) 51%,rgba(17,17,17,1) 60%,rgba(28,28,28,1) 91%,rgba(19,19,19,1) 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, rgba(76,76,76,1) 0%,rgba(89,89,89,1) 12%,rgba(71,71,71,1) 39%,rgba(44,44,44,1) 50%,rgba(0,0,0,1) 51%,rgba(17,17,17,1) 60%,rgba(28,28,28,1) 91%,rgba(19,19,19,1) 100%); /* IE10+ */
background: linear-gradient(to bottom, rgba(76,76,76,1) 0%,rgba(89,89,89,1) 12%,rgba(71,71,71,1) 39%,rgba(44,44,44,1) 50%,rgba(0,0,0,1) 51%,rgba(17,17,17,1) 60%,rgba(28,28,28,1) 91%,rgba(19,19,19,1) 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#4c4c4c', endColorstr='#131313',GradientType=0 ); /* IE6-9 */
}