We have a number of servlet-based applications. One general problem is that if the servlet container is down, the users get an error and nothing else. My idea was to write a page that we could interpose between the servlet app and the user. The page would check on the availability of the app, and if it was down, offer some static information that might be helpful. My first attempt used dojo.xhr("HEAD", ...) (setting the load function to assign the URL I was checking to document.location) and didn't work because the servlet container is on a different port.