Because there are thousands of links listed on this website, it's normal that you will occasionally find links that aren't working. As I cannot regularly check every link to see whether it still works or not I've written a short guide about what to do when you find a broken link.
NOTE: The Peace Corps website previously available here is no longer available. Please see this post and this post for advice on downloading the courses from that website.
1. Try to find the homepage from the website address
e.g. The web address of the broken link is:
But this address doesn't work, so start by deleting part of the link, starting from the left, until you reach the / mark, like so:
Perhaps this doesn't work either, so again, delete part of the link until the next / mark:
Sometimes website owners change around the addresses of their pages, and by using this technique you increase your chances of finding a working page. And then you can check if the page you want is listed somewhere else on the site.
2. Check Internet Archive
This is an archive of sites from 1996 to a few months ago. Even if the site has been deleted you may be able to find a record of the site you are looking for, although not every site will be archived. Pictures, audio and uploaded files are often lost but the text and the basic layout of the site will remain.
Copy the address of the link and put it into the 'Wayback Machine' to check. If that website has been archived you can look back at 'snapshots' of the site at different points in the past.
Note: Many blogs are not archived, by request of the blog authors.
If the site you are looking for is a Geocities website, there are various different archives you can check, including Internet Archive, Reocities, Oocities, Geocities.ws and Internet Archaeology.
3. Search on Google
Sometimes the website has changed address, or someone has uploaded the data to another website. Try searching for the website's name on Google, and if there are too many search results then try searching for the exact name enclosed in speech marks ("").