左の 5% を必要な色で塗りつぶすボディのグラデーション背景はどうですか?
http://jsfiddle.net/YwN8v/2/
body {
background: linear-gradient(to right, #183950 0%, #183950 6%, transparent 6%);
}
アップデート
グラデーションを作成するための優れたツールは次のとおりです: http://www.colorzilla.com/gradient-editor/、しかし、その出力から必要な値のみをコピーして貼り付ける方が良いです:
background: url(data:image/svg+xml;base64,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);
background: -moz-linear-gradient(left, rgba(24,57,80,1) 0%, rgba(38,69,90,1) 6%, rgba(40,71,92,0) 7%, rgba(255,255,255,0) 100%);
background: -webkit-gradient(linear, left top, right top, color-stop(0%,rgba(24,57,80,1)), color-stop(6%,rgba(38,69,90,1)), color-stop(7%,rgba(40,71,92,0)), color-stop(100%,rgba(255,255,255,0)));
background: -webkit-linear-gradient(left, rgba(24,57,80,1) 0%,rgba(38,69,90,1) 6%,rgba(40,71,92,0) 7%,rgba(255,255,255,0) 100%);
background: -o-linear-gradient(left, rgba(24,57,80,1) 0%,rgba(38,69,90,1) 6%,rgba(40,71,92,0) 7%,rgba(255,255,255,0) 100%);
background: linear-gradient(to right, rgba(24,57,80,1) 0%,rgba(38,69,90,1) 6%,rgba(40,71,92,0) 7%,rgba(255,255,255,0) 100%);