You can check the Net log and the Network log in the Web Console (Firefox/Tools > Web Developer) to see if content fails to load or possibly is blocked (file size is zero).

• https://developer.mozilla.org/Tools/Network_Monitor

Use Ctrl+F5 or Ctrl+Shift+R to reload the page and bypass the cache to generate a fresh log.

If you use extensions (Firefox menu button/Tools > Add-ons > Extensions) that can block content otherwise affect file transfer (Adblock Plus, NoScript, Flash Block, Ghostery, Blur, HTTPS Everywhere) then make sure that such extensions aren't blocking content.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Hold down the Shift key and left-click the Reload button
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Command + Shift + R" (Mac)

Clear the cache and remove cookies only from websites that cause problems.

"Clear the Cache":

• Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > "Use custom settings for history" > Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions (Firefox menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox menu button/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

I've tried all you suggested, and none of it worked. that page at: www.listia.com still opens like plain text, not html code. I'm not running any extensions. I tried running Firefox in safe mode (No adons). nothing worked. Firefox is using the default theme.

Control + F5, don't fix it. Control + Shift + R, don't fix it. deleting the sites cookies didn't work.

If you try to load the page's style sheet directly, will Firefox open it?

https://assets.listia.com/assets/homepage-35bb56d3ef09d90c9b6981efb731b1d7.css

It should appear as a "wall of text" starting with

/*! normalize.css v3.0.3 | MIT License |

If Firefox won't load the page, do you get any specific error message?

That page: https://assets.listia.com/assets/homepage-35bb56d3ef09d90c9b6981efb731b1d7.css Opens with no errors and it is plain text. No errors.

What does the Network Monitor shows for the CSS files?

Network Monitor? huh? :-/ Say that again in English... lol

I posted a suggestion about the Network Monitor in my first reply. The Network Monitor is one of the built-in developer tools (Firefox menu button or Tools > Web Developer) that shows what files are requested from the servers and the server response.

• https://developer.mozilla.org/Tools/Network_Monitor

Here is screenshot of it for you:

http://i60.tinypic.com/2cibolk.png

http://i62.tinypic.com/2yo9250.png

Hope it helps...

I found the problem. :) I had to reset Avast AV. Don't know how or why it was blocking some or most of those sites...

Thanks anyways guys for all your suggestions... :)