html - 另一个 div 的 div 中的 margin 属性

Question

html:

div id="wrapper">
        <div id="itro">
          <ul>
            <li>
            <h2> Title</h2>
            <p>This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content. </p>
           </il>
           <ul>

                <div id="logo"> <img src="image/bottom_logo.png" alt="logo" width="45" height="50" align="right">
                </div>

        </div>

CSS:

#wrapper
{
    width:850px;
    margin: 0 auto;
    background: #B3B3B3;

}
#itro
{
    width:550px;
    border: 6px solid #000;
    margin: 0 auto;
    position: relative;
    background:#E7E7E7;
    margin-top:70px; 
}

我想在#itro 上设置边距，但是当我在浏览器中看到它时，div id="wrapper"> 也设置了 top margin:70px;为什么？

Answer 1

CSS:

#wrapper{
    width:850px;
    margin: 0 auto;
    background: #B3B3B3;
    height:500px;
}
#itro
{
    width:550px;
    border: 6px solid #000;
    margin: 0 auto;
    position: relative;
    background:#E7E7E7;
    margin-top:70px; 
    float: left;
}

HTML:

<div id="wrapper">
        <div id="itro">
          <ul>
            <li>
            <h2> Title</h2>
            <p>This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content.This is dumy content. </p>
           </li>
           </ul>
            <div> <img src="image/bottom_logo.png" alt="logo" width="45" height="50" align="right" /></div>

      </div>

        </div>

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