The second part is using your naive friends again and having them try to find something. The on-going part of the problem is that web sites grow. There always seems to be something new that merits a new page. Keeping the topology rational requires attention if the site is not to grow randomly and become a haystack. Some of those links go off-site.
Nothing irritates a visitor more, and nothing is more of a nuisance to keep up to date.
Check your external links regularly, check them often, and try to find out if it's not working for a permanent or a temporary reason. At the next level, making your site work well means making it efficient for your visitor to access and traverse rapidly. This means loading pages quickly, which means dealing with the reality of current Internet delays. Moving billions of bits of images and text across the Web still works a bit like an old-fashioned bucket brigade. Web pages are broken down into tiny packets of information and then handed from one computer to the next until they finally reach their destination.