The Cookies controls are a bit hidden in Firefox 3.5. You will need to go Tools >> Options.. >> Privacy. From there under history select from Firefox will: Use custom settings for history.
Your screen will change and be similar to below. Click the Show Cookies… button to manage your cookies.
The Firefox Extension Guru's Blog 
Txs for this
thanks was trying to figure out how to do this
Saved my sanity. I thought they just removed it, I was running in circles trying to find it again when it was easy to find in previous versions. Mozilla’s Firefox help site was worthless in helping me find the cookie manager.
I wonder if this change causes more problems than it solves, I understand they might be wanting to prevent just any yokel from monkeying with cookie settings, but it makes it harder to clean up cookies too. I’m not certain, but the upgrade from 3.0.x to 3.5.x seems to have broken the cookies for some sites. Maybe it’s not the case, but it seems suspicious that, on at least one site, Firefox suddenly couldn’t remember my login immediately after I upgraded.
[…] I have the same problem except it's on every site I go to. Here are links you may find helpful: Managing Cookies with Firefox 3.5 The Firefox Extension Guru’s Blog Unable to "keep" Firefox 3.5 cookies – Piriform Community Forums Cookies […]
I had no problem finding the settings, but I DO have a problem with the lack of flexibility, and one other problem;
Firefox 3.5X keeps my cookies, but reports that they are not there, and each time I shut down the browser it de-selects the “accept cookies…” check box. This prevents me from being autologged into my.yahoo.com.
Firefox help website is arrogant, dismissive, narrow-minded, and not at all helpful. Do you have a solution for this?
I. M. Stumped!
I’m having the same problem. Every time I open, I need to go to “privacy” and ask it to accept cookies again. Which means that every session I need to log-in anew to about five sites.
I’ve replaced my FireFox software to no avail. Any ideas here?
What happened to being able to accept or deny cookies when visiting a site for the first time and then firefox remembering your choice?
Now you have to manually add exceptions which will be incredibly tedious.
This coupled with the ‘hiding’ of the cookie options makes me wonder what they’re playing at and has got me looking for a new browser
Anyone know how to copy the cookies file to a new computer?
On previous version I was able to deny by default all cookies and to allow only them for some sites. With new version I’, not able to do this. Is there a way?
I agree too. I used to keep a few selected cookies such as google, disallow third party cookies, and ask about others with the default answer of keep for this session. I don’t see how to do this anymore so I’m thinking seriously of winding back on version number and frezing.
I was wrong and I grovel.
It’s still there but it’s not so obvious.
Tools -> Options -> Privacy
Firefox will: ‘Use custom settings for history’
x Accept cookies from sites
Keep until: ‘Ask me every time’
using firefox, i’d like to close out of firefox but keep signed in automatically to Gmail and Livemail for hotmail, right now i think it dumps my “remember me” stuff cuz of deleting cookies? i don’t know
They actually bring back the option to delete cookies in version 3.6.3 Now you can find the option by just clicking clear recent history.
Can’t we remove them from the clear recent history itself ?
This is uncool from firefox. how come they hide this important settings, who get this idea?
[…] 10 Posts Uninstalling JAVA Console Add-onAdobe Acrobat vs Foxit ReaderManaging Cookies with Firefox 3.5YouTube: Auto Buffer and Stop AutoPlayHow To Remove Microsoft .NET Spyware ExtensionTip: Unexpected […]