Getting Username and Passowrd From the system

hi  
  i have   username  and  password  i enter it .  and  a checkbox  asking user  to remember the  username  and  pwd on this  system  and  login  into application  and  sign out.

 next time  i  login into application  i neeed  to get the username  and pwd   to be  filled  into the  textbox automatically  
 how  to  do it   . can  any one tell me    out
thank  you   

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