I've been a Mozilla and more recently Firefox user for a long time, but only recently noticed the availability of extensions. (I know :") ) I'm really excited by the extensibility, but cautious about the tie-in to a single browser development environment. I know Microsoft ignores this all the time, and unfortunately I'm finding more and more sites that seem to *require* IE to use. My question is, even though the underlying XML is "open" and "standard", doesn't the use of XUL lead to the same sort of "lock out" for users of typical "public" services, such as libraries who frequently have no choice (or even knowledge) of which browser to use? Is there anything that can be done, or has been done, to take these great extensions, and the tools to create them and make them coexist with or "embrace and extend" the IE universe?