That could be the cache in your browser, or a proxy cache somewhere between you and your webhost, or even a webserver cache on the webhost. It's annoying when that happens - I had the same problem this morning with some cached Java Applets, the only reliable way I could get the most up to date version was to close my browser completely and restart it. Refreshing, clearing the cache etc, just wasn't doing it. I'm still not sure what that was all about.

I always try to do my development on a local server - aside from the safety (do you want your visitors to see your mistakes?) and speed, it does ensure you don't get any caches interfering with your updates. I either run a webserver on my laptop, or on an old P2-266 I keep for just that purpose.