Unless you created a backup, they are gone. Is there something you need back? Cookies are created by the websites when needed.

Do you mean that you lost auto-fill form data as well? How did you delete the cookies? Did you use built-in means like "Clear Recent History"? *https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox A detail like a website remembering you (log you in automatically) is stored in a cookie. So by removing these cookies the website will no longer recognize you and you would have to login again. Saved form data (Form & Search History) is stored separately and shouldn't be affected by removing cookies. Cookies are stored in the cookies.sqlite file. You can check in Windows Explorer if there is a previous version of the formhistory.sqlite file available. *right-click: Properties -> Previous Versions *http://windows.microsoft.com/en-US/windows7/Previous-versions-of-files-frequently-asked-questions You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page. *Help -> Troubleshooting Information -> Profile Directory:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder *http://kb.mozillazine.org/Profile_folder_-_Firefox