影で浮き上がる固定ヘッダー

<div class="d03-11-06-stage">
          <header class="d03-11-06-header">
            <span class="d03-11-06-logo">FLOAT</span>
            <nav class="d03-11-06-nav">
              <a href="#" onclick="return false">サービス</a>
              <a href="#" onclick="return false">実績</a>
              <a href="#" onclick="return false">お問合せ</a>
            </nav>
          </header>
          <div class="d03-11-06-scroll">
            <div class="d03-11-06-body">
              <p>↓ 少しスクロールするとヘッダーが浮き上がります</p>
              <div class="d03-11-06-block"></div>
              <div class="d03-11-06-block"></div>
              <div class="d03-11-06-block"></div>
              <div class="d03-11-06-block"></div>
            </div>
          </div>
        </div>

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