Imagine that the URL needed to start your deployed web browser application was:
Option 1: Create a shortcut on their desktop that resolves to the URL.
You can even create the shortcut on your desktop, then drag and drop it into an e-mail. The e-mail recipients can then drag and drop it from the e-mail onto their desktops. When they click on the shortcut on their desktop the web browser will be started.
Option 2: Create a simplified startup HTML file.
If you create an HTML file named App.htm (say) on your web server that contains HTML like this:
Then the users only ever need to type into start the application.