Sometimes "deleted" pages may say "404" or "Not found" on the page, but actually return a 200 status code in the page header; so it's good to use a proper header-checking tool to double-check.

有时“已经删除”页面可能会显示“404”或者“没有找到”，但事实上是在页头显示200状态代码；因此最好使用合适的页头检查工具再三核查。

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Header: the page header shown on the page; not the same as the head element.

header：页面上显示的页眉；与head元素不一样。

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If you look at the body of the HTML page near the bottom of the listing, you see that this header is literally in a header tag-one of the new HTML elements in HTML 5.

如果您查看清单3底部附近的HTML页面主体，您将看到这个标题实际上位于一个header标记中—这是HTML 5中的一个新HTML元素。

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He succeeded brilliantly: 114 detailed maps in line with the text, hundreds of margin notes, a header on every page showing time and place, and 11 appendixes that illuminate military, economic and political concepts of the time.

FORBES: Magazine Article