I have extended the RacerX theme to add custom css for the hover event for list items in action menus on BWC modules. In BWC modules there isn't much of a difference between the item the mouse is over and the rest of the items. We wanted some styling to make it more noticeable. I changed the behavior to be more like the action menus on sidecar modules so that the item being hovered over has its background and text color change.
My question is how do I force it so that user's browsers are forced to update the cached version of the css file? In testing I noticed that I wasn't seeing the changes I made until I went to my browser's settings and told it to clear the cached images and files. Is there a way that I can change the versioning that gets added to the file when it is included so that the user's browser will automatically recache the file? I don't want to have to make my users manually clear their cached images and files in their browser.