Question : Port 80 somehow got blocked.  Cannot visit any http websites.

NOTE: I am sponsoring this problem for a friend of mine simply because he cannot access this message board right now.  

It has been a while and a few people, myself included, have tried helping him.  Someone eventually figured out that port 80 (http) was being blocked on his system.  He's running Windows 98.  We already looked and removed an irrelevant virus from his registry and system32 folder.  That doesn't mean we removed any other program that was blocking this port.

The cause is unknown.  Just one time he couldn't go to anything but cached websites using any browser.  The broswer would get "access denied" errors on nearly any site.  Before knowing it was a port blocked, we removed temporary net files (including cookies).  He is able to open locally-saved html documents sent to him by other means.  He just simply cannot access http.

I have given him a simple port blocker and unblocked, blocked, then again unblocked port 80 and it had no effect.  Possibly, this program could not detect if the port was blocked or not.  As far as I know, he does not have any real programming compilers so I doubt giving us any source code to check the status of the ports would do any good.  

I will be forwarding your and his replies through a chat client.  Because of this message board's rules, I do not think I can allow you to directly interact with him as that would betray the clever point system going on here.  For simplicity, consider me having the problem, and I'm somehow magically able to access the messgae board :)

Answer : Port 80 somehow got blocked.  Cannot visit any http websites.

A few questions:

Your sure it's JUST port 80? He can ping, get email, FTP, etc? If not, it's a network issue. Can he ping www.google.com? Can he ping 216.239.39.99?

Can he visit sites by typing in the IP address in the address bar? Try "216.239.39.99" If that works it's a DNS problem, change DNS server info.

Is he using a proxy? If so, try without.

Has he checked device manager?

Hsve you done a complete virus scan on that PC with updated definations?