I have often experienced while developing my web applications that pressing F5 or refresh doesn\'t produce or refresh the proper result. But when we hit Ctrl
F5 reloads the page from server, but it uses the browser's cache for page elements like scripts, image, CSS stylesheets, etc, etc. But Ctrl + F5, reloads the page from the server and also reloads its contents from server and doesn't use local cache at all.
So by pressing F5 on, say, the Yahoo homepage, it just reloads the main HTML frame and then loads all other elements like images from its cache. If a new element was added or changed then it gets it from the server. But Ctrl + F5 reloads everything from the server.