Sometimes we put password for security keyguard but any how we get error to unlock the phone. As per my experience following tricks will help you a lot

1.Try the password ‘12345’.It is default password for all Nokia phone security keyguard.
2.If it did not work try to regain password you changed and try entering by switch off –on your phone.
3.Finally just remind what you have done while locking keyguard. And use same method to unlock the phone e.g. If you are listening music through head phones and locked the phone then use same method. Connect headphone and enter the changed password to unlock. My case this was worked. Also other tricks are like while charging, Sim card removal and insert etc.

Other than above traditional way below are some technical-online tricks will help you-

1.Go to following site. Go to “Forgotten your Nokia security code? Click here”. Enter your IMEI number(You will find this number on your mobile bill or on handset box)

http://www.trycktill.com/eng/unlock_swe.asp

Once you click then in below window you will get new security code like 3644263089. Enter and unlock security keyguard. There is other site also which same as above. Below is its link

http://www.unlockitfree.com/

2.Sometimes you will get code generated from above sites in following manner
#pw+3644263089+1# .To use this code you should use keypad *key to enter the alphabets and arithmetic signs. e.g. press * 3 times to enter ‘p’ character.

3.Try both the ways to enter the security code above. That means if you get only code then use’ #pw+’ before and ‘+1#’ end of the number.
Below is method which is suggested me by Nokia help desk
First type 11111 then 22222 up to 99999 repeating for 3, 4, 5,6,7,8 digits finally 00000.
Then take battery out and wait a good 10 minutes this resets the code. Turn your phone on and repeat the same process above in the same order and wait 10 more minutes. Once turn it on it will ask for your security code. As you have followed the steps the code will now be to the default of ‘12345’ then enter your new code to change it.