What was Petunia's Howler all about in Harry Potter?

I read Deathly Hallows. I must have missed it...I never saw where they explained Aunt Petunia's howler that she received. What did it mean?

What was Petunia's Howler all about in Harry Potter?
Well if I recall correctly the howler said "Remember my last, Petunia." The letter that Dumbledore left with Harry on the steps I think had nothing to do with it. I think "his last" was the letter he wrote personally to her, when she wrote a letter after Lily got accepted into Hogwarts.
Reply:Basically, Petunia knew the charm on Harry only worked when he was around family. When she took him in, Dumbledor made her promise she would always allow him to stay at their house. It was in the last book, like other people have said. :)
Reply:In the first book, Petunia got a letter from Dumbledore that said they must keep him until he turns 17 and she made a promise to do that. That's what the howler was reminding her of.
Reply:Related to a previous book, when dumbledore sent Aunt Petunia the howler telling her that she promised to keep Potter.
Reply:It was not mentioned in Deathly Hollows, it was mentioned in the Half-Blood Prince. Dunbledore sent a letter to Petunia telling her that for Harrys protection he had to stay with a blood relative since it was his mothers spell that was protecting him.
Reply:Yup, Petunia was to keep Harry Potter in the summer until he came of age.
Reply:it was about the letter that was put with harry when he was leaft at her door. that her blood helps keep him safe till he is on his own.