For the benefit of others who might find this thread in a Google search and not be informed, let me say that while the scareware shown in this thread is indeed a joke, a variant of it exists that is more "Mac-like" in appearance and can automatically download an installer package, which may automatically launch if browser settings permit. It's known by many names, such as MacDefender or MacSecurity. For more details, read the first part of the following link.
To avert needless panic, be aware that there has never been a virus in the wild that affects Mac OS X since it was released 10 years ago. The handful of trojans that exist can be easily avoided with some education and common sense and care in what software you install:
The first section of that link deals specifically with the MacDefender/MacSecurity/MacProtector issue. I encourage you to read it.