Well, there you go! But this is interesting. According to the link on that page, two ISP's are blocking http://archive.org. However - notice this is http, which is the old, insecure web standard that might be expected to give the security errors you received.
But there are apparently no blocks on https://archive.org which is the secure web standard that should be used today.
However, notice that the two ISP's who blocked the http version are giving SSL errors for the https version. Are you using one of those ISPs?
Site report for archive.org
Report incorrectly blocked sites on UK ISP and mobile networks
www.blocked.org.uk
But there are apparently no blocks on https://archive.org which is the secure web standard that should be used today.
Site report for archive.org
Report incorrectly blocked sites on UK ISP and mobile networks
www.blocked.org.uk
However, notice that the two ISP's who blocked the http version are giving SSL errors for the https version. Are you using one of those ISPs?