Internet Explorer 7.0 / PC

Scenario: Internet Explorer 7.0, Flash Content and the Mootools Library
Symptoms: When Flash content is playing (FLV/SWF) Mootools animation appears to stutter and/or conflict with Flash in IE7.
Resolution: Several people have noted that there is an issue when trying to animate with Mootools and other JS libraries whilst playing Flash content. It turns out that this could possibly be related to your preferred method of Flash embedding. Many opt to use the SWFObject ( API, but for most of us, in an effort to reduce JavaScript payload, others opt to use classes available to them in their existing Javascript libraries, i.e. The Mootools Swiff() class. However; A List Apart has done some extensive research into cross-browser Flash embedding and go on to say that most of these embed methods, whilst standards compliant, aren't truely cross-browser compatible. Once again we need not look to far to see the culprit. Internet Explorer's implementation of the object tag. For true cross-browser compatibility A List Apart recommends using the nested-objects method :

In tests this has resolved many issues of playing Flash content in IE7

Firefox 2.0 / Mac

Scenario: Firefox 2.0 on the Mac'
Symptoms: Flash content not appearing (but audio playing), and 'peak-a-book' issues with z-index'd layers.
Resolution: ( and others started to note this interesting little conundrum back in 2007. An issue actually confirmed by Mozilla themselves ( Yet today I find it still plagues me. Basically if you have an underlying layer that isn't opacity o or 1 the Flash will not show, and oddly enough this is only on the Mac' version of Firefox2.

The answer is to simply detect Mac/FF2 and kill any fancy overlays (set them to opacity: 1 or 0) underneath. Not very conducive for design, but ensures your Flash content is viewable by all.

Further Reading :