Apple's knowledgebase articles are an excellent source for troubleshooting aspects of Mac systems and Apple's software. Apple links to them from numerous locations on its Support Web site, but recently a number of people have noted problems with accessing the knowledgebase articles.
In some instances when loading an article, the page will state that the requested information cannot be found on Apple's servers, but at other times the connection to the site has been refused or encountered errors with too many redirects or other problems that prevent the articles from loading.
When you are able to connect but get the error indicating the information cannot be found on the server, first try refreshing your browser. In the past few weeks people have found that when using Safari the pages do not always load the first time but do so on subsequent attempts, so simply refreshing should fix the issue.
For the other instances where the knowledgebase articles do not load, you can try clearing your browser's cache and otherwise reset Safari's features using the Reset Safari option in the Safari menu, but in addition try turning off Safari extensions in the Extensions section of the program's preferences, and also try troubleshooting Internet plug-ins by disabling those in the Security section of the preferences. If either of these result in the pages loading properly then you can further investigate which plug-in is causing the issue for you.
In many cases these problems are with misconfigured cookies for the site, which might happen if Apple changes an aspect of the site and does not have it update the cookies in your browser. In these cases the site should function after resetting Safari, but if not then go to the "Privacy" preferences and click the Details button. Then search for "Apple.com" followed by selecting and removing the entry for it that includes the cache, cookies, and local storage.
After this is done, try reloading the knowledgebase article, and it should open properly. However, if you are still experiencing problems then at least for the short term you should have success accessing the knowledgebase by using Firefox, Chrome, or another Web browser.