Firefox – Install Silverlight for Mozilla Firefox without administrative privileges

Wikipedia on Silverlight:

Microsoft Silverlight is a web application framework with a scope similar to Adobe Flash. Version 2, released in October 2008, brought additional interactivity features and support for .NET languages and development tools.

So basicly, it is a competitor to Flash that uses .NET languages and is more focused on developing interactive web applications, rather than animations and movies.

Currently, Silverlight is only available for Windows and OS X, but there is an open source implementation being developed by the Mono team entitled Moonlight.

How-To-Geek had an article about installing Flash 9 in FireFox manually. Follow the steps to install into your profile not the All Users profile, as that will probably be locked down by the Corporate IT Department. I haven't tested it with Flash 10 myself.

I would warn however that your IT department may well frown upon installing Flash 10 this way. Depending on the organisations policies, manually installing software could be breaking the companies Acceptable Use Policy.