position 固定的属性，是全局的。和DIV层次无关。
<!DOCTYPE html><html lang="en"><head> ???<meta charset="UTF-8"> ???<title>Title</title></head><body> ???<div style="background-color: aqua">标记1</div> ???<div style="background-color: brown ;position: fixed; ???????bottom: 0;right: 0" >标记2</div></body></html>
结果如下：
<!DOCTYPE html><html lang="en"><head> ???<meta charset="UTF-8"> ???<title>Title</title></head><body> ???<div style="background-color: aqua ;height: 100px"> ???????标记1 ???????<div style="background-color: brown ;" >标记2</div> ???</div></body></html>
<!DOCTYPE html><html lang="en"><head> ???<meta charset="UTF-8"> ???<title>Title</title></head><body> ???<div style="background-color: aqua ;height: 100px"> ???????标记1 ???????<div style="background-color: brown ;position: fixed;right: 0;bottom: 0;" >标记2</div> ???</div></body></html>
<html> ---- position
原文地址：https://www.cnblogs.com/zhuhai-wmy/p/8351083.html