Is there a way to hide the subject field of messages which appear in the top right corner of the screen when I receive an iMessage on my computer? I know there is a way to hide it on messages that come to my iPhone. Is there a way to do the same on Mac OS X?
To clarify on what @Macmaniman posted, you'll want to change a setting with your notifications. To do this, go to your Settings app > Notifications (upper right corner) > Messages (in the left-hand column). Uncheck Show message preview, which will hide the message previews (or subject fields, as you refer to them).