hello tigrca, from your troubleshooting information it appears that you have a user.js file present in your profile which can often cause problems because it is used to override your custom preferences. please try this: go to the firefox menu ≡ > help ? > troubleshooting information > profile folder - "show folder", then a new window will open up. in this window look out for a file named user.js - delete or rename this file and restart firefox afterwards.

in case this didn't help yet, please also try to reset firefox, which will keep your bookmarks and passwords...

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

Philip and cor-el, Thank you both for your suggestions. Funny, but somehow typical: After unsuccessfully trying every solution I could dig up and then asking for assistance here, I shut down for the night. Lo and behold, this morning the issue is no longer present. I'm both happy about that and a little exasperated, you know? So I cannot say if either of your solutions would've helped, but in the event of a recurrence I will revisit this page and let you know. Again, thanks much, tigrca01

I just encountered the problem of not being able to sign into my Yahoo! account with my Mozilla browser (Dec. 4, 2014.) I tried the steps of clearing my cookies and cache and even upgraded my Mozilla browser to the latest version, with no luck. Note: I could sign in to my Yahoo! account with Google Chrome and with IE 11.

This morning, after "sleeping on it," I wondered if my "Do Not Track" settings (no tracking) on my Mozilla browser was causing the problem of "cookies rejected." First I tried signing into my Yahoo! account with "no tracking" settings through Do Not Track on Mozilla. I couldn't sign in. Then, I disabled the tracking on Do Not Track and tried signing into Yahoo! with Mozilla. Bingo! I could sign in. I have now reset Do Not Track for "no tracking." Others may wish to try this solution if the steps provided through Mozilla support don't work.

Edit 13 Dec 2014: Correction regarding my "Do Not Track" settings. Actually, it was an Add-on I had enabled on Firefox: PrivacyChoice TrackBlock 2.2 which resulted in my not being able into my Yahoo! account (cookies rejected) through my Firefox browser. I disabled it, shut down Firefox and rebooted Firefox (with PrivacyChoice TrackBlock 2.2 disabled) and I could log on. Earlier this week I enabled Privacy Choice TrackBlock 2.2 and had the same cookies rejected problem. Instead, now, I use AVG Do Not Track (I have AVG as my anti-virus software) and I have removed PrivacyChoice TrackBlock 2.2.

Everyone, the problem re-appeared this morning. So... Philip, I tried renaming user.js as you described. It did not solve the problem. I did not try the reset option you mentioned.

juanaquena, I tried changing the settings for Do Not Track, both in Firefox and also my Privacychoice Trackerblock. The problem persisted!

cor-el, Your solution appears to have done the trick. I restarted Firefox in Safe Mode, but the problem persisted. Since I had recently begun using the Space Fantasy theme, I reset that as you instructed to the Default and was able to sign-in at Yahoo while still in Safe Mode. So, I closed and restarted Firefox regularly, and was still able to sign-in at Yahoo. It seems the Space Fantasy theme add-on was the culprit, although I'm not clear on why it interfere only sometimes and not always. Oh well, I'll just stick with the default theme.

Thank you all for your help! tigrca01

I wouldn't expect a lightweight theme (Persona) to be able to cause this issue (an extension could), so I assume that either the problem corrected it self and hopefully stays that way or rebooting the computer or restarting Firefox a few times has cured it in case security software is involved.