Residential said:
I use font types which render an ugly result. In addition i like the thin
line style of the non cleartype rendering.
So in other words, there's no real practical reason other than cosmetic
(of your liking). Bear in mind there's also people with vision problems
that use cleartype or other addons for a reason. I for one would be
wondering why your page didn't render correctly (i.e. to the settings I
set in my browser like a larger font or custom font).
Ofcourse you're free to design a website to your own liking. That's not
the point. But if you're going to enforce something like this, you may
lose viewers.
If you really really really want to, render it to an image file and
display that. Or use something like flash, which is not ruled by those
kinds of settings.