From my observation browsers cache css and image files. If changes were made, you need to hit "force" refresh button if you want to see updated version. However I am not able to verify if browsers also cache text content? For example:
If you have a web page with:
<body> foo </body>
A user visits it, then you change it to:
<body> bar </body>
Does the user still need to "force" refresh to see updated text content?