This is a simple application that will allow you to open XML files in Firefox. You need two things to use this: a file browser (Astro, for example) and Firefox. Browse to any XML file with your file browser, open it, and select "XMLViewer for Firefox" from the list of options presented. If you don't already have Firefox installed, you'll be prompted to download it and be taken to the market page. Firefox has a good XML viewer built in. This does nothing but pass through an "open XML file" request to it. That's it.