For a number of months now, Safari has been exhibiting an irritating behavior when viewing YouTube videos.  While browsing around the site “alternate” versions of videos would seemingly randomly begin playing outside the normal YouTube player.  In much the same way that a run-of-the-mill MPEG would show in the browser window.  That is, with a dark gray background and a video player centered in the middle of the window.

Searches around the Web return hints that other users have experienced the same sort of behavior, and the Safari plugin ClickToFlash is often included in the reports.  In fact, the ClickToFlash website tells that the plugin makes YouTube's H.264 formatted versions of its videos available to Safari in favor of the Flash versions.

“YouTube also offers H.264 videos…you get access to those same, higher quality videos.”

Without doing any real in-depth troubleshooting, it would seem that something between the combination of ClickToFlash and Safari is causing a little mixup between browser and plugin.  The result is that a URL to the video is exposed.  The result is often frustrating since what took place to “get” the alternate version of the videos is not clear.  But there are now steps that can reasonably reproduce the situation.

1. 1.Load YouTube.
   

2. 2.Search for something.
   

3. 3.Click a video.
   

4. 4.While it's loading, click the browser's back button.
   

5. 5.Alternate video.
   If the video doesn't load with the back button, click it again.
   

This behavior has been experienced with Safari for Mac version 5.0 and ClickToFlash version 1.5.4.