JavaScript Caching Hack

If you change the HTML and the CSS of a page there is a decent chance that a user will get the new HTML but not the new CSS. This is especially true for sites with high usage and users that come back to the site several times a day. If they only get the new HTML but not the new CSS then the site will break, the user will get confused, and you will look unprofessional. On the development site of this the problem is already solved. Having a Dev server as a place to test code is standard practice but how does this translate to CSS?