Can you fully utilize a VB ActiveX Control's features with Javascript or only with VBScript?
You can use "JScript"(MS Javascript, so that means Internet Explorer's interpretation of Javascript) and "VBScript" to do what you want to do with your ActiveX controls.


...will a webpage with a VB ActiveX control (and VBScript) be fully functional if displayed in Netscape Communicator?

Netscape (making yet another bad decision...) will never allow any microsoft product to run in their browser(that is, activex controls) As far as I know there are some Java "wrappers"/"containers" that allow activex controls to be run through Netscape. I can't remember the name of the product but Netscape definitely should of sucked up their pride and enabled ActiveX functionality in their browser.

Personally I wouldn't allow an ActiveX control be downloaded to my machine from the inTERnet. An inTRAnet is a different story though; you've got a much better chance at not downloading a malignant control.