Vertical styled headshots or horizontal styled headshots? Also know as portrait or landscape, these are two examples of both. Both achieve different results, let me explain.
The headshot to the right of this paragraph is an example of the classic headshot, where the subject's head is positioned at the top or middle of the frame. Any casting director from the late 90's to now will tell you this is a classic format.
The headshot to the left of this paragraph is an example of a "fairly" recent style of headshot known as landscape or just "horizontally shot". The subject is positioned to either side of the frame, slightly off center. As early as 2003, there was a growing trend for actors to get their headshots taken this way, mainly to stand out from the crowd. These headshots also provide actors the opportunity to come across a bit more "situational" in their photos, because from this perspective you can see more of the background and environment in which the actor is in. This can be a double edged sword. If you are submitting to Law and Order: LA but have your horizontal headshot taken next to a white picket fence, as opposed to a metal fence, that may not be the best "situational" place to put yourself in. Another example, you are submitting for a role of a wall street banker, but you submit a photo of yourself in a hooded sweatshirt next to a swing set, or you're wearing a flannel shirt sitting in a pumpkin patch, these are both good examples of how a "situational" headshot can go against you. Use your head, know your type, submit accordingly. Both styles of headshots are fine, and relevant. Just know what style you want before you start shooting with a headshot photographer. To see some great examples of both styles of headshots, visit Descanophotography.com to see how a professional headshot photographer can get you shots like this.