HtmlDialog is a method on the IE class, not on the browser class. HtmlDialog is not available for the Firefox browser.
_You'll need to do something like _
IE myIEbrowser = Browser.AttachTo<IE>(...);
myIEBrowser.HtmlDialog....
_Not _
Browser myGenericBrowser = Browser.AttachTo<IE>(...)
myGenericBrowser.HtmlDialog(.... <- This won't work because the HtmlDialog doesn't exist in the base Browser class.
This is for WatiN 2.1