TLS is the successor to the SSL security protol, which is what is used for secure connections on banking and other such sites. Mot sites use SSL 2.0 or 3.0, so having TLS unchecked usually doesn't cause any issues. Unless the sites you frequent all use TLS, the "page not founf" error is being displayed for a different reason. (Could you list a couple of the sites for comparison?)
My only other comment would be that you should have a firewall running. When you say your ISP provides one, that means they have one you can download, install, and run, not that you are currently protected behind a firewall. You can either take the one they offer or use something along the lines of ZoneAlarm, which has a free version.
Hope this helps,
John
Win2000pro /SP4 .. Abit AN8 Ultra mobo .. AMD 64 bit 3500 processor.. Antec 450 powr sply ..56k dialup ..US Robotics V92 Modem .. Frequently get "Page Cannot be Displayed" I did search the forums for the above quote, didn't find what fits me. Went Tools> internet options> advanced, noticed TLS 1.0 is unchecked. LIKE to KNOW WHAT it DOES. Oh yeah, I have AVG anti-virus with automatic updates, Free AdAware, Paid Winpatrol (very good helper) , also running trial ewido . My ISP folks claim that they provide a firewall.

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