JSF has it's own configuration context parameters, which may optionally be specified, to further tune or configure applications. These context parameters are set in the web.xml file of your application. Various JSF implementations, such as Mojarra, also have their own configuration context parameters.
Default is Production
When the PROJECT_STAGE is set to Production, and a resource is within its cached duration, then the web browser can avoid going to the server at all for the resource. If it's beyond the duration, or the user has pressed the Refresh button, then the browser may request if the resource has been updated, which can either return an HTTP 304 code saying that the resource is still valid in the browser's cache, or it will return an HTTP 200 code and serve out the resource, if it has been updated.
When the PROJECT_STAGE is set to Development, the cache duration is ignored, so the browser will always request if the resource has been updated, and use the HTTP 304 and 200 accordingly. So, caching is not completely disabled, as it can still avoid downloading the resource, but it will still communicate with the server.
Default is 604800
This parameter is specific to Mojarra's JSF implementation. The default is about 10 minutes, which is not really that long. It's recommended that production applications specify a longer caching duration, for example 2 weeks. Again, this only applies when the PRJECT_STAGE has been set to Production, and allows the browser to avoid any communication with the server, in regards to cached resources. There is no means for setting different cache durations for different resources, this globally applies to all resources.