Redirects are what happens when you try to go to a page and you go somewhere else or are “redirected” to a different page. There are a lot of reasons that this might occur. The page may have been removed. It could have been incorporated into a different page. The domain name might have changed. There’s a long list of legitimate things cause this. Most web servers will redirect to a “Page Not Found” or a “404”. This happens and doesn’t have major SEO consequences although it’s not the best for user experience.
According to Wikipedia: “The practice of employing fake 404 errors as a means to conceal censorship has also been reported in Thailand and Tunisia. In Tunisia, where censorship is reportedly severe, people have become aware of the nature of the fake 404 errors and have created an imaginary character named “Ammar 404” who represents “the invisible censor”. “
Another type of redirect that has negative consequences is a “soft 404”. This can happen when the web server doesn’t send you to the page you requested and sends you not to the designated 404 page but to some other page which still isn’t what you requested. Our client’s custom ecommerce storefront created nearly 500 of these “soft 404” errors that Google reported. Needless to say their movement towards optimization was slowed until this problem was solved.