I don't think you can set the style declaratively on the control as you have done, you can add style attributes programatically as outlined here.
The other thing is the moj AdRotator does support Target just like the built in ASP.NET one, however the target attribute is not valid in xhtml, so the runtime probably won't render it because we have it configured only to render valid xhtml by this setting in Web.config:
<xhtmlConformance mode="Strict" />
This probably blocks the rendering of the target attribute in both our control and the asp.net version. If you remove the config setting it should render the target attribute, but then your pages won't validate agaisnt the w3c validator.
Hope it helps,