This is generally used on tablet-based apps to display a block in a modal fashion: the user must interact with the dialog or dismiss it before continuing in the app. On the iPad, this is implemented by the Pop Over Control.
The block will be added above the current view as a popup. Until the popup is dismissed, it will be the only thing the user can interact with.
This can be either pixels or a percentage. A default fixed width will be used if this is left blank.
An optional title that will appear at the top of the popup.
This color will be used to tint the title area of the popup.