This topic is: Forcing the Browser
First, I want you to realize I'm not advocating drug use — the sixties are over. What I am advocating is not pissing off visitors to your site by making ridiculous demands.
There are a fair number of sites that want visitors to make their browser window a certain width, to change the default fonts, and other such nonsense. What these sites forget is most people don't know how to change the default fonts (just ask any Internet Service Provider). What's going to happen is obvious. People will say, "The heck with it" and go surf elsewhere.
It's the same thing with plug-ins. Unless you're a movie, art, or record site don't force people to load plug-ins to view your site.
Don't alienate your visitors.
(This text is from Web Pages That Suck)