When an IFRAME has the "display:none" style applied, it is inaccessible from the window.frames collection.
If the style is applied after window.onload is fired, it is accessible. Tested with Safari 1.0.3 (v85.8) and 1.2.3 (v125.9).
The IFRAME with style "display:none" applied is from the frames collection.
The IFRAME contained in a DIV with style "display:none" applied is from the frames collection.
The IFRAME with style "display:none" applied during window.onload is from the frames collection.
The IFRAME (ZIPish) with style "display:none" applied during window.onload is from the frames collection.