How does JSF cache CSS?

I have 2 CSS files as below. style.css is getting 304 Not Modified. But default.css is always getting 200 OK. Why is default.css not being cached?

<h:outputStylesheet library="css" name="default.css"/>
<h:outputStylesheet library="css" name="style.css"/>

I have tried including number of external multiple CSS files into XHTML .I always go with the basic approach to insert CSS into XHTML.I insert the following lines on the index page of your project. It always works fine.

<link rel="stylesheet" type="text/css" href="file1.css" />
<link rel="stylesheet" type="text/css" href="file2.css" />

It is possible that the default.css style is being provided by the server with some sort of document header that prevents caching. This may be out of your control, but if not you could inquire if the server has some specific rule(s) via htaccess or another configuration that prevents the browser from caching (or caching for a very short time).

If default.css is a dynamically generated document, the header could also be created dynamically by the language that creates the actual css document on the server.

There are tools like Fiddler and browser plugins like Live HTTP Header that allow you to inspect the headers of a file requested by the browser.

The browser itself can also have caching turned off but if two unique files with the same extension are acting differently it's probably not a browser setting.