Type about:preferences#advanced<Enter> in the address bar.

Under Advanced, Select General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?

Then restart.

When you want to click a link, first check it in the small window display at the bottom of the screen. Does it look okay? After clicking, do you end up on that page?

After I turned off Use Hardware Acceleration and restart, I saw no other problems, but the site didnt load.

When I look at the window from a link to a site that works, it looks okay and I end up on that site. For the one site that doesn't work, the link in the window looks same to the links that work, but I end up on Yahoo.

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

it may help u

Thanks for the fast answer, but it still doesn't work. Will wait for the malware check to complete.

It finished now, didn't find anything.

reinstall FF in safe mode

Thank you very much, it's working now.

welcome

Well, sadly it seems like it's not that easy. After I reinstalled it yesterday in safe mode, I could load the website. But today, the yahoo error returns. Of course the first thing I did was to try to reinstall it in safe mode again. In the safe mode, after installation, it worked fine, but after a reboot to normal window, the error is back.

And is it normal, that the folders (32-bit Windows) C:\Program Files\Mozilla Firefox or (64-bit Windows) C:\Program Files (x86)\Mozilla Firefox don't exist after uninstalling firefox? Because they aren't there. As long as I have FF, the folder exists.

Can somebody help?

The number of sites not working anymore is getting higher, every few days there is one more site I use regulary that doesn't work anymore and now sends me to the "Yahoo Page not found" page. Still need help.

Do a malware check with several malware scanning programs on the Windows computer. Please scan with all programs because each program detects different malware. All these programs have free versions.

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
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender:
  http://windows.microsoft.com/en-us/windows/using-defender
• 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.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked
• https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware

The last three days after I made the scans it worked fine, thank you. If this problem occurs again, I will write here.