When I click on the anchor URL, firebox pulls up the page, but a lot of pages are directed to 401 page of the site even though they ARE valid, because if I copy it in the address bar and hit enter, the URL works just fine. Is that a problem with SpyGlass? I see quite a few sites are like this. I can provide you the list of the sites too.

Can someone explain this or help solve this problem? I am not sure if this is being reported before.

I am using SpyGlass (latest professional version)
and firefox (latest version)

There is such a problem indeed - only with some URLs with faulty CMS. The thing is that there is a bug in the Safari browser which requires the query we send from within the software to contain "ht%6Dl" instead of "html". So the query we send is "ht%6Dl" in order for it to work for Safari users. It works for practically all URLs and browsers, but SOME web-pages with specific CMS (faulty in a way) do not support it. So basically you get to a 401 page from within SEO SpyGlass, but firefox transforms ".ht%6Dl" to ".html" and once you hit enter again it goes to the actual page. This is exactly what is happening, so you understand - but we a thinking of some workaround for that...