Originally posted by Black Wolf
It's not exactly wrong either. If you're using commas for lists, then ", and" is wrong, but if you're using it to denote a break in the timing of the sentence, then ", and" is acceptable.
You should use a comma before the last item of a list, except where it would cause confusion.
Example: "I am going to the store to get eggs, butter, and milk." A comma is used before "and"; no confusion there.
Example: "I would like to thank Mr. Smith, the mayor, and my friend Joe for their help". Here there's confusion as to whether Mr. Smith and the mayor are the same person. If they're not, then the comma should be taken out: "I would like to thank Mr. Smith, the mayor and my friend Joe..." If they are, the sentence needs to be reworded. Though if I were writing the sentence I would reword it even in the first case so as to keep the comma in its proper place.