I've never tested it on Netscape, but on mozilla.
It's not fully compatible, for example validation controls are not
rendered, so validation is performed only server side, unless you use
third party controls.
What's more, to render the html correctly, you must include some code in
the web.config.
Finally, you have to do some extrawork to make it almost fully
compatible with non-explorer browsers.
HTH
Stefano Mostarda MC
Rome Italy