[fix bug 1047287] Firefox OS page Adaptive Phone section throwing error in IE9

https://bugzilla.mozilla.org/show_bug.cgi?id=1047287

IE9 does not support transitions, so it uses the fallback animation method (which requires the IE specific stylesheet for the `filter` properties on background images). This checks if the `filter` property is present, and if not just assumes to use `background` instead.