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Actually, you could do this with Netscape Navigator, sorry to burst your bubble.

It's just images in a row scaled to different sizes. The effect is amazing, but the idea is simple.

Well, to get pedantic, I think the original Navigator fizzled out before CSS was truly supported. Not sure you could do it without it.

You don't need CSS to do this, just positioned images (which you can do with layers, or even with a blank image above the main one).