Q: I'm seeing old pages (such as last months charts) when I view NWR. Why?
A: Your ISP, browser, or another server along the route to your machine probably has the page cached.
What's a cache?
A cache is basically a place of storage, wherein, your ISP, and many servers along the path to your machine (including your browser) store pages for a certain period of time to make the web seem 'faster'. The content will generally expire within a few days, but sometimes become 'corrupt', and doesn't expire, so you see old pages.
Depending on what browser you use, you can clear the cache on your machine. Internet Explorer calls this cache 'temporary internet files', and has a method to clear them under options.
Sometimes you can also force your ISP to refresh its cache by 'refreshing' the page using the refresh button, and by pressing Ctrl-F5 (force refresh).
If none of that works, just wait a few days and your ISP 'should' clear its cache!