How do I load XUL from a Web site?
XUL may be loaded either from your local file system, installed as chrome, or loaded from a remote Web site. XUL that is loaded from a remote site is subject to security restrictions so you cannot call native components or read files and preferences. You can perform these operations only with signed code or code installed as chrome.
To use remote XUL, just place the XUL file and associated scripts on a remote site. Ensure that your Web server is configured to send XUL files as the content type 'application/vnd.mozilla.xul+xml'. If your server is not configured correctly, the XUL will either be displayed as plain text or the user will be prompted with a download dialog.