clear属性与浮点数直接相关。属性值：
无-默认。允许两侧都浮动
左侧-左侧不允许有浮动元素
右侧-右侧不允许有浮动元素
两者-左侧或右侧均不允许使用浮动元素
initial-将此属性设置为其默认值。阅读有关初始
继承-从其父元素继承此属性。了解有关继承的信息
<html>
<head>
<style>
img {
float: left;
}
p.clear {
clear: both;
}
</style>
</head>
<body>
<img xx_src="https://static.pexels.com/photos/69372/pexels-photo-69372-medium.jpeg" width="100">
<p>Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum </p>
<p class="clear">Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum Lorem ipsoum </p>
</body>
</html>