Disable GeckoFX confirm messages

I am using Gecko Web browser version 21.0.1 and .net Framework 4.0 in my windows application.

When I navigate to certain web pages I get Pop up confirm message:

This web page is being redirected to a new location. Would you like to resend the form data you have typed to the new location?

How can I disable this kind of messages?

So far I have tried the following settings, but they didn't help:

GeckoPreferences.User["security.warn_viewing_mixed"] = false;
GeckoPreferences.User["plugin.state.flash"] = 0;
GeckoPreferences.User["browser.cache.disk.enable"] = false;
GeckoPreferences.User["browser.cache.memory.enable"] = false;