Every time you change external files like CSS (Cascading style sheets), you have to clear cache on the browser to see the changes. Clearing cache on application load is a a frustrating step for users. Here is a solution:
Add a questions mark and string to the end of the UTL of the CSS fil, example "?version=xx.xx.x". On application load, the browser will think that this is a new CSS file, but when it parses it it will get the file name with out the "?flush=1".