Currently Being ModeratedJan 24, 2013 5:05 AM (in response to baruchsienna)
Click once, then twice on the HTML widget in iBA. this ensures you have the placeholder selected rather than the entire widget. Then go to the inspector>graphic inspector, and adjust the transparency option of the placeholder there.
You can place the html over anything you like that way – but watch that it doesn't overlap with other interactive stuff - such as galleries or glossed text. iBA might allow it, but it doesnt work on the iPad.
Hope that helps.