One of the web sites I check on fairly regularly has a message that is seen if it is viewed without Cascading Style Sheets (CSS):
If you can read this, either the style sheet didn't load or you have an older browser that doesn't support style sheets. Try clearing your browser cache and refreshing the page.
Well, it's actually right: the style sheet didn't load. I don't want it to load. I want to read the page in my color scheme, with the text at a legible point size, and not have the content all squished over to one side with a big column of advertising taking up useful space.
Other sites have similar, often more insulting, messages. "Hey, go get a real browser." only worded slightly better (listing a few browsers, generally none of which I choose to use). It's not that I can't view it the way the site author thinks I should, it's that I do not desire to view the site that way. With a single click I can view it "as designed" and at many sites I have and clicked right back to get something I can stand to look at.
The whole freaking point of CSS was to separate the information content from the decorations and let people choose to see the content as they prefer. It was not meant to inflict some so-called web designer's idea of kewl on the site viewer. But that seems to be the way it gets used.
A simple "No style sheet loaded" message would be fine. The "You are not getting the full experience of this site..." sort of message (which covers CSS, javascript, and Flash abuse) makes me think of some documentary that called it "the Vietnam experience" rather than a war. Most site "experiences" seem to be like the "Vietnam experience": a poorly thought out, ugly, bungled mess.