Height:100% for !BackgroundIframe doesn't work in quirks mode, even on IE8.   That was causing a problem where a !DateTextBox promptMessage interfered with Calendar interaction.   Fixes #12020 !strict.
Height:100% for !BackgroundIframe doesn't work in quirks mode, even on IE8.   That was causing a problem where a !DateTextBox promptMessage interfered with Calendar interaction.   Fixes #12020 !strict.

git-svn-id: 674a2d6b1e32e53f607eb824547723f32280967e@23274 560b804f-0ae3-0310-86f3-f6aa0a117693

harbalk/delite,harbalk/delite,kitsonk/delite,kitsonk/delite,Sam-Cummins/delite,Sam-Cummins/delite