关于置换和非置换元素_html/css_WEB-ITnose

在之前的浅谈HTML中的块级元素和内联元素中了解到了内联元素一般是不能设置宽高的，但是也有特殊。比如img是内联元素，但可以设置宽高，这肯定让不少人迷惑。这样我们就要引入HTML中置换元素的概念（非置换元素在w3c中没有给出明确的解释，姑且我们就把除置换元素外的元素当作非置换元素吧）。

a) 置换元素：浏览器根据元素的标签和属性，来决定元素的具体显示内容。
例如：浏览器会根据标签的src属性的值来读取图片信息并显示出来，而如果查看(x)html代码，则看不到图片的实际内容；标签的type属性来决定是显示输入框，还是单选按钮等。 (x)html中的、、、<select>、<object>都是置换元素。这些元素往往没有实际的内容，即是一个空元素。</p> <p>置换元素在其显示中生成了框，这也就是有的内联元素能够设置宽高的原因。<br /><br />b) 不可替换元素：(x)html 的大多数元素是不可替换元素，即其内容直接表现给用户端（如浏览器）。</p> <p>例如： <label>label中的内容</label> 标签<label>是一个非置换元素，文字label中的内容”将全被显示。 </div> <div class=""> <ul class="m-news-opt fix"> <li class="opt-item"> <a href='/htmldaima-269016.html' target='_blank'><p>< 上一篇</p><p class="ellipsis">Sass变量、嵌套_html/css_WEB-ITnose</p></a> </li> <li class="opt-item ta-r"> <a href='/htmldaima-269018.html' target='_blank'><p>下一篇 ></p><p class="ellipsis">高手们，我这代码运行时为什么出错_html/css_WEB-ITnose</p></a> </li> </ul> </div> </div> </div> <div class="g-title fix"> <h2 class="title-txt">人气教程排行</h2> </div> <div class="m-rank u-dashed mb40"> <ul> <li class="rank-item"> <a href="/htmldaima-274978.html" title='如何生成一个调查问卷_html/css_WEB-ITnose' class="item-name ellipsis" target="_blank"> <span class="g-art-count fr">230次</span> <span 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