Reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Press and hold Shift 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 the cookies from sites that cause problems.

"Clear the Cache":

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

"Remove Cookies" from sites causing problems:

• Tools > Options > Privacy > Cookies: "Show Cookies"

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

• Do NOT click the Reset button on the Safe mode start window or otherwise make changes.

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

Do a malware check with some malware scanning programs on the Windows computer.
You need to scan with all programs because each program detects different malware.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender: Home Page:
  http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• http://support.kaspersky.com/viruses/solutions?qid=208280684

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

Reload using Ctrl+F5 that should override cached items and may work.

• see Firefox can't load websites but other browsers can
• and Firefox and other browsers can't load websites

Note the list of things to check including clearing the DNS cache. And clear the cookies for the MSN site

• Clear cookies and site data in Firefox_delete-cookies-for-a-single-site

Does IE work ok ?

What is the site address ? is it http://msn.com

Try http://65.55.206.228

Possibly there are performance issues with the site. For me it redirects to a local site, but I did see data loss when I recently directly pinged the address, but some sites block pings anyway. This site will give some sort of status report and has comments http://www.isitdownrightnow.com/msn.com.html

Thank you for your comments, I'll try them. Yes, IE does work, I was using msn.com and I tried the number address you listed.

Ok so it is a Firefox related problem, cookies and cache probably, unless IE ONLY works with the IP number address, but not the ordinary link.

Problem resolved by deleting cookies and clearing cache. Thanks