Elena's front door has glass panel's in it, in every subsequent episode there are no glass panel's in her front door. This is because the pilot was filmed in Vancouver, whereas the rest of the show was filmed in Georgia.
The Salvatore boarding house looks completely different from what it does in the rest of the series. This is because the pilot was filmed in Vancouver, whereas the rest of the show was filmed in Georgia.
The sign by Mystic Falls cemetery says it was established in 1792, but later episodes state the town was built in the 1860s.
Elena's house address is different. In S1 E1 Elena's house number was 935. In season 2 Elena tells an ambulance that her address is 2104 Floyd Street. This is because the pilot was filmed in Vancouver whereas the rest of the show was filmed in Georgia.
According to Elena's phone, the first day of school is September 7th, but September 7th, 2009 was Labor Day. Schools would have been closed.
During the history class when they are talking about he Battle of Willow Creek the blackboard says the battle was in 1865, but throughout the rest of the show it is always said that it happened in 1864.