Today mistakenly i deleted my offer letter which i rcvd yesterday pls help me?

Did you look in the mail trash? That's where your deleted messages go. And if you emptied the trash, it's permanently gone. And further, if it's the "offer letter" I think you got, you need to just forget the whole thing. You did not win any lottery or free money. Microsoft, Yahoo, or any other person or company does not give money away anonymously.