Start Firefox in Safe Mode. If it still comes up;

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Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• TDSSKiller - AntiRootkit Utility
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Did this fix your problems? Please report back to us!

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.

• 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.
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: 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.

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

See also:

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

Two other users have posted this problem today:

• Everytime I launch firefox today or try to go to a bookmarked site it goes to www.Neo.com (unsolved)

• how do i prevent neo.com from opening (unsolved)

In another thread, a user discovered that using an old bookmark for Yahoo mail can cause this problem. Aha!

Many users have discovered all kind of problems and glitches with Yahoo! mail in Firefox when using an old bookmark or old home page URL saved before Yahoo!'s recent server changes.

If you are accessing your mail either of those ways, I suggest clearing your Yahoo cookies and entering through the main page to get a better address for your current mail server.

To remove your Yahoo cookies -- save any pending work first -- call up the Cookies dialog while viewing any page on yahoo.com (or your Yahoo site). You can use either:

• right-click the page > View Page Info > Security > "View Cookies"
• Tools menu > Page Info > Security > "View Cookies"

In the dialog that opens, you can remove the site's cookies individually.

Then go to one of these Yahoo addresses and click on login or mail from there:

• Yahoo home page: https://www.yahoo.com/
• My Yahoo page: https://my.yahoo.com/
• General mail redirect: https://mail.yahoo.com/
• AT&T users: http://att.yahoo.com/
• Other country sites (not on .com): the main Yahoo page for your country

You can save the new address if it works, replacing your old bookmark or home page, as applicable.

It appears that the problem is gone and I don't know what solved it partly because the problem was intermittent. I did several things as suggested by FredMcD, Cor-el, and jscher2000.

I ran Malwarebytes Anti Malware, Windows Defender, IOBit Malware Fighter, Advanced System Care--all free versions, went to Firefox safemode--a new one to me--, checked on my Firefox/Tools > Add-ons >.

I was disappointed that I can only click on one of your "solved the problem" buttons because I wanted to give credit to all of you for your quick and terrific help, quite unlike many help sites where people respond to a question and then end their answer with: but I really don't know because I've never used that program...product... or whatever. (Lumberjocks is another great site for high-quality help--but probably not for help on computer issues.)

jscher2000; Don't you hate it when someone moves, but leaves no forwarding address?

Iroquois; Good luck. And if the problem should come back (fingers crossed), ask for help.