If you maintain your own site you’ve probably run into overzealous caching of CSS by either the web server, ISPs, the browser or some combination of all of all three. Here’s a quick-n-dirty way to bust the caching of CSS without compromising performance:
<?php echo '<link rel="stylesheet" type="text/css" href="/css/index.css?<?php echo(time());?>"/>
The above results in:
<link rel="stylesheet" type="text/css" href="/css/index.css?1492810248" />
The highlighted portion tricks whatever’s caching the .css file into thinking that it has been updated and forces download of a new one to the client. Using the current time (seconds since the Unix Epoch [January 1 1970 00:00:00 GMT]) keeps you from having to generate your own versioning scheme. You can do the same for .js files as well.
And that’s all I have to say about that.