Do you share the same ISP? Many ISP's use a caching server and you might need to wait for the server to update. On another note, it can be the browser. If you have visited the site before, your computer may be storing a cached version of the page. The reason they get the new page is exactly because they have never been there before and their computer has no reference to look at so it must pull a fresh copy.
I am not saying that it is your browser for sure, but it is always a possibility. I would say it is either a browser issue or your ISP is caching the page.
Clear your browsers cache or press Crtl+F5 while visiting your site and see if that clears things up. If not then I might suspect your ISP is doing the caching.