checkbox is still checked, but the css class is turned back to the uncheck... What happens exactly when I press F5? Is the rhtml page rebuilt??? or what, and where the checkbox information is stored (since it has kept its checked state) in params, session or ...?
when you press F5 you will usually get a new petition of the page to the server. It depends on browser cache configuration anyway. Maybe images are not reloaded and .js by default wouldn't either, but rails appends a chunk of numbers to gracefully reload js without wiping the cache.
So, when the server gets the new petition it will reload the action and, as you say, 'rebuild' the rhtml (assuming you are in development environment and didn't change the defaults).
About the client side values, such as the selected check boxes, it's your browser the one populating the values again after hitting F5. On Firefox you can force a full reload with Ctrl+F5, and not sure if on IE was Shift+F5.