This message appears in your browser's address bar because the website you are trying to reach has been configured to restrict the number of downloads that can be made from it in a given period of time, or the files that you are trying to download are very large and the connection fails as a result, or too many attempts are being made to access in too short a time (due to how the site is interacting with your connection via our server that manages off campus access).
Normally the easy solution to this issue is to leave the site for 10-15 minutes, and refresh your browser and try the access again. Clear the cookies and cache and browsing history from your browser and restart the browser. Some browsers also allow you to perform a total refresh of the browser if simply clearing the cache does not work for you. Wikipedia includes a useful artilce that gives basic instructions on how to clear your cache etc. in different browsers: Cache clearing and disabling. If there is still a problem write to ejournals@lib.cam.ac.uk.
