html - why does a Body Tag shift if you have a child with a top margin

Question

Welcome To Ask or Share your Answers For Others

html - why does a Body Tag shift if you have a child with a top margin

posted Jan 31, 2022 in Technique[技术] by 深蓝 (71.8m points)

html - why does a Body Tag shift if you have a child with a top margin

I have spent a good chunk of my time to figure this out. In case you have a div with some margin on the top. The body position as per the chrome dev tools start from the point where the div starts from. Basically it doesn't consider the margin for the offset. Though it does considers the same for height calculation.

Eg -

<body>
    <div> my content my content my content my content my content my content my content my
    </div>
</body>

I have created a jsFiddle for the same -- http://jsfiddle.net/tusharmathur/kW4v4/

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…

1 Reply

深蓝 · Answer 1 · 2022-01-31T07:05:31+0000

Because of collapsing margins: http://www.w3.org/TR/CSS2/box.html#collapsing-margins

This means that, when there is no padding or border getting in the way, two elements in the document flow will share their margins, like one big happy family.

body is absorbing the top margin of div.

This has been part of spec for aeons.

You can add 1px of padding or border to body to stop it from happening.

More details on collapsing margins can be found here - https://developer.mozilla.org/en-US/docs/Web/CSS/margin_collapsing

Categories

html - why does a Body Tag shift if you have a child with a top margin

html - why does a Body Tag shift if you have a child with a top margin

Please log in or register to add a comment.

Please log in or register to reply this article.

1 Reply

Please log in or register to add a comment.

Just Browsing Browsing

Most popular tags