In book four, during Priori Incant tem, Voldemorts victims came out in reverse order. BUT, James came out BEFORE Lily. That would mean that James died AFTER he killed Lily and it said all over in the books that he killed James first. (Fixed in later versions of the book)

After Hermione dropped Muggle Studies, she said she had the same amount of subjects as Ron and Harry. But she still had (besides the mandatory ones) Arithmancy, Care of Magical Creatures, and Ancient Runes. Which is more then Harry and Ron who each had only Divination and Care of Magical Creatures.

When Dumbledore was telling everybody about the TriWizard Tournament during the start of term speech he said: "We have worked hard over the summer to ensure that this time, no champion will find himself or herself in mortal danger." (Don't you think facing a Hungarian Horntail that breathes fire forty feet would classify as 'mortal danger'? Even if there were trained hit wizards nearby you catch one of those flame-bursts and you’re a corpse before the wizards can do anything.)

In book 2, it says that Moaning Myrtle haunts the U-BEND of the toilet. In book four, it says that she haunts the S-BEND of the toilet.

In Book four Fudge, Dumbledore, and Moody are talking ABOUT Crouch. But instead of Fudge yelling to Dumbledore, it says: "said Crouch angrily". He wasn't in the room...they were talking about him, not with him.

Portkeys are supposed to transport whoever is touching the portkey at a prearranged time. But, Harry and Cedric were transported to Voldemort and the Death Eaters the SECOND they touched the TriWizard cup. Don't you think that sounds a little bit too...coincidental? Also, couldn't Moody/Crouch have just made Harry's pillow or something a portkey and transported him when he went to sleep at night? Wouldn't that have saved all the effort of guiding him through the whole TriWizard tournament?