Have you double-checked the Options page to see whether the logins have been deleted or whether the feature was just turned off?

Windows: "3-bar" menu button (or Tools menu) > Options Mac: "3-bar" menu button (or Firefox menu) > Preferences

In the left column, click Security. Then on the right side, check:

• Remember logins for sites has a checkmark to enable it
• Anything listed when you click the "Saved Logins" button?

Have you noticed any other settings or add-on issues? For example, if you used Firefox's "Refesh" feature, then many settings would return to defaults and some add-ons may be removed.

Did Firefox perform a Refresh?

Unless it was interrupted in progress, you should find a folder on your desktop named Old Firefox Data. Inside would be a semi-randomly-named folder with freshly updated files. Do you see anything like that?

If so, we'll suggest how to rescue key files or completely restore the earlier profile folder.

I am not having the restore point of earlier versions. Therefore i am here. I am too much sad now. All details i have been lost.

I have not find name Old Firefox data. This happen with me when i loose. I have open the saved login details and my system automatically turnoff due to low voltage., After 1hour when i open my system again i see my all details are loss. I don't know how it happen?

When you say "all details" I'm not sure what you mean now. Originally you said your bookmarks and history are still there.

If your system crashed, it's possible that some of your Firefox data files became corrupted and may not be recoverable. It's also possible that your Firefox profile was locked and at the next startup Firefox created a brand new one -- but in that case, you wouldn't have your prior Firefox bookmarks and history. Could you clarify the situation?

Have you already tried restarting Windows a couple of times to try to release file locks and make sure that any repairs Windows might need to do after this kind of crash have been completed?