-> Tap ALT key or press F10 to show the Menu Bar

-> go to Tools Menu -> Options -> Security -> place Checkmark on "Remember Passwords for sites" -> click OK

Check and tell if its working.

Already tried this but still doesn't work.

btw thnx for the alt key tip.

Make sure that you do not run Firefox in permanent Private Browsing mode.

• https://support.mozilla.com/kb/Private+Browsing
• You enter Private Browsing mode if you select: Tools > Options > Privacy > History: Firefox will: "Never Remember History"
• To see all History and Cookie settings, choose: Tools > Options > Privacy, choose the setting Firefox will: Use custom settings for history
• Deselect: [ ] "Permanent Private Browsing mode"

See also:

• http://kb.mozillazine.org/User_name_and_password_not_remembered