Changing background opacity of page

So I’m trying to change the background opacity of the page so that when I link the url through to an app I have on my tablet it will be transparent, leaving only content showing (i’m using an iframe to display weather content from forecast.io). I’ve tried changing the alpha on the row, column, and widget box down to 1% and can’t seem to have any luck. I tried some various css codes I found around this forum as well and had no luck with those either.

Any help would be appreciated!