Looking at this quote:
Can we achieve a shadow effect on a div using just CSS?
And also referencing this one:
How can we make a new div display a shadow effect for the user?
It appears that you are inquiring about the possibility of creating a "shadow" effect around the inner div
through CSS.
The settings page on Chrome uses CSS3's box-shadow
property to achieve this:
-webkit-box-shadow: 0 5px 80px #505050;
box-shadow
is compatible with these browsers: http://caniuse.com/css-boxshadow
The cross-browser CSS code for this effect is:
-webkit-box-shadow: 0 5px 80px #505050;
-moz-box-shadow: 0 5px 80px #505050;
box-shadow: 0 5px 80px #505050;
You can check out an example at http://jsfiddle.net/XHAbV/
If you require support for older versions of Internet Explorer, you can use CSS3 PIE to simulate the box-shadow
in those browsers.
For information on how to achieve this using JavaScript (like a modal window), please refer to another comprehensive answer provided.