Overriding the outer div

Hello,
If I have main.html like below
<div id=“main”>
<div id=“header”>
</div>
<div id=“content”>
------------ Here is where my subpages are shown
</div>
</div>

This theme is common across all pages but if I have a sub page “user.html” that requires a change to the outer div “main” like set the background color to black then how do I accomplish this change without affecting other pages.

Thanks,

Add an ID to whatever it’s parent is (body?)

<body id=“user”>

Then for css:

#user #main { background:#000; }

Probably the simplest approach. The parent ID lets you override specificity quite easily.