is it a windows server? I use to have windows, and for some reason, when i uploaded new content, the old content would show for a few hours, even if someone, who hadn't been on the site before, went onto it
must have been the server proxy, but then changed to linux, so never found out if it was the proxy
No, it's your browser. To speed up page loading your browser remembers where you have been and stores that information in a temp directory on your harddrive.
Next time you visit a page the browser will know you have been here recently and instead of downloading the page again from the internet it will just pull the files from your harddrive which conciderably speeds up the loading time for the page.
A tiny drawback is when you have made recent changes to the site. Your browser does not bother to check the internet it just pulls the page from your harddrive. It can display the entire page for you even if you are not connected to the internet.
Hitting the refresh button a couple of times "usually" forces the browser to load the page from the internet again thus displaying the updated page on your screen.
edit: I just saw the part about the windows proxy. Should take more care in reading. No experience with that.
I do however know that the above is correct and I have helped countless of angry customers who told me the server was broken to see the light