Handling the Marvel Cinematic Universe has to be a bit of a difficult task. There's so much going on, so many story lines that overlap that you have to pay super close attention to not overlook certain aspects and make them all fit in properly.
Honestly, they've done a really good job of handling that stuff. Still, as there are with any movie there are going to be some oversights along the way.
Below is a video that highlights nine such mistakes that slipped into the final versions of the film and have been identified by the masses...did you notice them?