Which security software (firewall, anti-virus) do you have?

A possible cause is security software (firewall,anti-virus) that blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

I use straight-up Microsoft -- Windows Firewall with Advanced Security and Microsoft Security Essentials. I turned-off the firewall and stopped "real-time" protection but it still acts the same way. I disabled the firewall in my DSL modem as well and no luck. I'm stumped.

What does the net log show for retrieving the CSS files (reload the page via F5)?

• Web Console (Firefox/Tools > Web Developer;Ctrl+Shift+K)
• https://developer.mozilla.org/en/Tools/Web_Console

I have the output in a text file but it's 55k characters. How can I post it?

http://pastebin.mozilla.org

Thanks cor-el... I hadn't ever had an opportunity to use PasteBIN before...

Here's the web console output: WebConsole output

hello, see line 25:

...default.css was not loaded because its MIME type, "text/html", is not "text/css"

the webserver is not configured correctly, so it sends the wrong file-format for stylesheets. this is an error that can only be corrected by the websites itself - please try contacting them about that issue...

Some stylesheets appear to be blocked:

The stylesheet http://demandware.edgesuite.net/aaea_prd/on/demandware.static/Sites-fein-Site/-/default/v1376733798084/lib/jquery/css/jquery-plugin.css was not loaded because its MIME type, "text/html", is not "text/css". @ http://www.cpofein.com/on/demandware.store/Sites-fein-Site/default/Default-Start?ref=em20130806
The stylesheet http://demandware.edgesuite.net/aaea_prd/on/demandware.static/Sites-fein-Site/-/default/v1376733798084/css/default.css was not loaded because its MIME type, "text/html", is not "text/css". @ http://www.cpofein.com/on/demandware.store/Sites-fein-Site/default/Default-Start?ref=em20130806
The stylesheet http://demandware.edgesuite.net/aaea_prd/on/demandware.static/Sites-fein-Site/-/default/v1376733798084/themes/default/css/site.css was not loaded because its MIME type, "text/html", is not "text/css". @ http://www.cpofein.com/on/demandware.store/Sites-fein-Site/default/Default-Start?ref=em20130806

Yes! That's it! I use "HostsMan" and HostServer ((Website) to "block" ad sites. HostsMan uses automatically-downloaded lists of ad sites to create HOSTS file entries with IP addresses of the localhost (127.0.0.1 ad.adsite.com). HostServer then intercepts 400 Errors and displays a friendly message: "Blocked: ad.adsite.com"... One of the lists that I use has "demandware.edgesuite.net" in it and when that is blocked, I have this problem. I couldn't tell this was happening because the "blocked" message is only displayed if the URL in the address bar is blocked and not when a blocked site is used to provide stylesheets.

When I disabled Windows Firewall and MSE, it never occurred to me that HostsMan was blocking as well and I never expected a useful site being included in ad lists.

Cor-el, thank you for taking the time to help me out!!! I'm sorry that I didn't think to disable HostsMan when troubleshooting and before posting. I'm glad that it didn't take you long to figure it out.

Thanks again!

Blocked: demandware.edgesuite.net

Hi! I Have a problem With mozilla, if i try to access with this site <possible spam link removed - c> or other sites he gave me troubleshoot errors