My clients tells me that when he views his web page online, the pages appear different than when he views copies of the same files offline, even when using the very same PC and browser.
My client does the day-to-day updating of his web pages, working with offline copies of the html pages (using CoffeeCup Free HTML Editor) (he NEVER touches the CSS sheet). He then uploads the amended files using CoreFTP Lite. Once or twice a year, I (using a different PC) make bigger changes (CSS, DIV'S etc.) by downloading the online files (again using CoreFTP), making the required changes, and uploading them with CoreFTP. My client then downloads these files from online, to his server's hard drive, ready for him to make the day-to-day changes, and upload them again.
Now, whilst I fully appreciate that in web design there are issues about browser compatibility, what I don't appreciate is that when my client views the web pages online (the 'live' version), and then compares them to the same (offline) pages that he's just double-clicked on his server PC, there are differences, the biggest being that the navigation panel, positioned at the right online, appears over at the left in his offline versions of the files.
Perhaps I need to add that a)I myself do not see any difference between my copies of the offline files and the ones online, and b)both he and I have cleared our browser's cache out, many times.