About CSS to solve the problem of two sides and so high

A time ago the company needed a backend management system, the left side is the navigation bar, the right is the content area. However thick just started with JS to control, but when the page coconut too long, there is a single thread with JS, loading is slow, there will be a process, find a lot of methods are not resolved. Finally, try to use CSS to finally solve. Let's see.

This is just an example.

The content of that part is long, listen to that there,

Let's see the code.

　　　　

. aa{
Background:pink;
Float:left;
width:200px;
padding-bottom:2000px;
Margin-bottom: -2000px;
Text-align:center;
}
. bb{
padding-left:200px;
Background:green;
padding-bottom:2300px;
Margin-bottom: -2000px;
Text-align:center;
}

AA, BB represent two sides respectively. It's going to happen.

About CSS to solve the problem of two sides and so high