Comment 3 for bug 1031059

This is by CSS-design. CSS in a document does not apply to an iframe inside that document. This is a CSS design decision.

This does not mean that Fogger should not recursively go through all frames inside a webpage and apply CSS to each frame.

Whatever Frogger decides to do, there is a way out right now: Javascript.

Lets say you wanted the following CSS done to the frame "canvas_frame":
.myclass { background-color: "#ffffff"; }

Do the following in Javascript:
var doc = document.getElementById('canvas_frame');
var firstmyclass = doc.getElementsByClassName('myclass')[0]
firstmyclass.style.backgroundColor="#ffffff";

If there is more than one myclass, you will want to recurively go through doc.getElementsByClassName('myclass') and apply the backgroundColor.