Sorry about the thread necro-bump, but it looks like I was wrong:
https://bugzilla.mozilla.org/show_bug.cgi?id=432371Silverlight doesn't work on most sites because there was a change of behavior in Firefox 3 that causes the plugin to not yet be loaded when silverlight.js attempts to determine the installed version of the plugin.
There are two variations of this script: one using <object> to embed the plugin, one using <embed>. The one using <embed> still works (which is why microsoft.com/silverlight works), but the one using <object> doesn't work.
So, yes, you still have the same situation where everyone has to update their copy of silverlight.js, but it appears that my explanation for why it fails on Firefox 3 wasn't accurate.