IMPORTANT NOTE: The current version of ClickOnce will only work properly in Internet Explorer. In particular if you try to download using Firefox the following error message will appear:
"Cannot Start Application. Cannot download the application. The application is missing required files. Contact application vendor for assistance."
Microsoft are working on cross browser support for ClickOnce - if you're interested read more here
A patch for Firefox that will enable it to run ClickOnce properly is available here