The first two links actually are redirected – i.e. www.flickr.com/oldscollege redirects me to https://www.flickr.com/photos/oldscollege. So when Page Optimizer goes out to those links it gets given a 301 or a 302, so it feeds that information back as a broken link since we can’t be certain if the page we were redirected to were what you intended. For example, if you linked to a blog post from a sister college, and that college took down the blog post and redirected to a different page, you probably wouldn’t still want to link to that page. You may want to update the links so they are pointing to the final destination rather than the redirected url.
For the last two, I am not certain why they are listed as not available. I will have our development team explore why. My suspicion is that they are pages that require you to be logged in to view. When I access the first link, the page is mostly empty. The second link asks me which of two sites I want to go to.
As to whether this will impact your SEO, the answer is “no”. Most experts these days do not believe that serving broken links affect your SEO ranking. Since Google’s algorithm is a black box, only people at Google know for sure, but you should be fine. My suspicion is that you would only really be penalized if you were chronically serving a large number of bad links. Broken links do affect your user experience so we lumped this under the overall experience of optimizing your page.
Thanks I’ll fix up the twitter link for sure. The next one is to a google site that my IT Department created. I’ll ask them about the redirect.
The last 2 both link to our internal system called Banner. It is the current student portal if that helps at all and yes they need to be logged in on those pages, but they are landing pages where they can login.