As is old news by now, the new Adobe.com is live, and they've done a great job. In my mind, definitely eclipsing either the old Adobe.com or Macromedia.com in terms of design. However, the demons of Flash bite again, and come with a huge helping of irony since Adobe is the purveyor:
You must be on a mac. Looks fine in my FF.
Linux, actually. But regardless of the platform, their site still doesn't look right because of their own software.
I'd put my money on it being the fault of the browser in this case. Internet Explorer has a similar layering issue, where it layers the cursor and some other controls over all dynamic layers, which causes the cursor (or control) to show when they ought to be hidden by a JavaScript menu. The Flash player just requests space from the browser… If the browser grants that space only in the topmost layer, that's not exactly the plugin's fault.
The answer is WMODE…. ;-)
Beyond the W3C specs comes the question of "what draws which parts of the page?" For browser extensions, browsers started by telling a Netscape Plugin which rectangle of the screen to draw into. Later some browsers (starting with IE4/Win, later moving to most Mozilla & Firefox, maybe Opera) added the ability to pipe plugin content right into the browser's own compositing buffer, and this routing would be triggered by a WMODE value in the OBJECT/EMBED tags. This allows the browser to overlay a DHTML menu upon a video without the flashing as browser and plugin each try to draw directly into the same screen area. (If you remember early digital video days, then think "directToStage" with QuickTime.)
Most browsers in use now support integrated drawing of extended content via WMODE routing, but some do not. I'll drop a pointer to your blog entry here at webfeedback at adobe dotcom so they can see that some were surprised at the lack of feedback in a minority browser.
jd/adobe
This may or may not add much to this discussion, but this issue occurs using Firefox 1.5.0.3 on Mac OS X and Windows when using Flash Player versions prior to 6,0,67,0.
Subsequent versions of the Flash Player appear to be unaffected.
There are also issues with IE7beta2 and both the top menu and the table border images.