Solve the gap between img and parent element

Recently, when I was working on an H5 page, I suddenly discovered a problem. I used a div to wrap an img. When previewing on the mobile phone, I found that there was a gap between the image and the div.

The first reaction at that time was whether the spacing was not set to 0, so I previewed the code:

　.active img {

　 　width:100%;

　Margin: 0;

　　}

<span style="font-family: 'Microsoft YaHei'; font-size: 14px;">　后来浏览了一些技术文档，发现了问题所在，原来是因为在H5文档声明下，块状元素内部的内联元素的行为表现所致，简单地说就好像块状元素内部有个看不见的没有宽度的空白节点。</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">而不设置vertical-align属性，vertical-align默认是baseline。</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">现解决方案有如下两种：</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">1.第一种最直接的解决方法是：</span><br><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">设置img的标签：vertical-align:bottom </span><br><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">修改后的的代码：</span>

<span style="font-family: 'Microsoft YaHei'; font-size: 14px;">.active img{</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">　　width:100%;</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">　　margin:0;</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">　　vertical-align:bottom;//top和bottom都可以</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">}</span>

<br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">2.由于baseline是设置行内元素(inline)或者表格单元素(table-cell)的垂直对齐方式，所以可以将img转换成块级元素。</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">第二种方法：display：block，把父元素的font-size设为0</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">修改后的代码：</span>

<span style="font-family: 'Microsoft YaHei'; font-size: 14px;">.active img{</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">　　width:100%;</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">　　margin:0;</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">　　display:block;</span><br><span style="font-family: 'Microsoft YaHei'; font-size: 14px;">}<br></span><em id="__mceDel"><br></em><span style="font-size: 14px; font-family: 'Microsoft YaHei';">.active{</span><br><span style="font-size: 14px; font-family: 'Microsoft YaHei';">font-size;0;</span><br><span style="font-size: 14px; font-family: 'Microsoft YaHei';">...</span><br><span style="font-size: 14px; font-family: 'Microsoft YaHei';">}</span>

Summary: This is my first time writing an essay to record every bit of my work experience. I may not be good at writing, so please give me more guidance. ​