Browsers use different of caching files, so you want to ensure that you files will not be cached, apart from setting your servers right, here is a little javascript function that will add a random parameter at the end of the url
// Cache buster.
var cacheBuser = function (url) {
// Check if query already in url.
if(url.indexOf('?') != -1) {
// Check for '&' as the last character.
if(url.substring(0, url.length - 1) === '&'){
return url + '_r=' + Math.random() * 5;
}
return url + '&_r=' + Math.random() * 5;
} else {
return url + '?_r=' + Math.random() * 5;
}
};