Running Windows XP Home Edition ver 5.1.2600 SP2 build 2600, my son cannot
access web pages requiring a log in.  He's using both Internet Explorer and Firefox
browsers. Regular pages load fine just URLs that require logging in won't load. He
gets that standard IE error msg like when your network is down that says "This Page
cannot be displayed". He asked Dad to help so I checked all the IE Options that deal
with security and privacy.  I matched all attributes to my laptop (XP HOME same build)
that can access pages requiring a login and matched each feature under ADVANCED
tab.  All attributes for CONNECTION and WIRELESS configuration match up fine. What
might I be overlooking?  Thanks,

See if this article covers the problem you are encountering.

http://support.microsoft.com/kb/884488/en-us

Thanks, that link was helpful. I have SP2 installed and those firewall settings are selected (for http and https) as they should be.  I was having trouble accessing https sites and pages with SSL protection. What I then found was that I had Norton AV partially uninstalled. The laptop came from Dell with 6 months of Norton. When it expired I downloaded AVG by Gristsoft and installed it and uninstalled Norton. The uninstall left some firewall settings in place that must have conflicted with Windows Firewall. I delected all references to Norton and I'm now able to access https sites.  Thanks much.