To prevent clicking the submit button again, one could use a little bit of (client-side) Javascript. Some change to the page should happen when the onSubmit event triggers, something that happens on many other sites, too. Some sites simply disable the submit button, annoying all users with temporary network problems, because you simply can not re-submit the form after a network outage. Some other sites change the label of the button to something like "please wait ...". A third category of sites injects or unhides a little piece of HTML that overlays the page at least partly and either asks the user to wait or simply shows an animated "loading please wait" GIF.

Monks without an enabled Javascript engine in the Browser would see no difference when the Javascript is done right, the other ones would see at least a faked sign of life.

Alexander