2. Confirmation that direct message has been sent appears as layer over the top of the page.
Twitter provides a subtle, unobtrusive notification messages, e.g. when a direct message is sent. The confirmation appears as a layer with a white background over the top of the page, covering the page header, and unfortunately, not providing a more obvious "Close" link to dismiss the message. The message can be easily dismissed by clicking anywhere in the div, but that's not readily apparent.