I am currently dealing with echo submissions from what I believe to be the browser. I am able to see from my webserver logs that I receive both a POST and GET submission. This problem occurs infrequently enough that it is very difficult to reproduce, but often enough to have several people comment about it's negative effect (they receive an error page rather than the desired page). An example page can be distilled down to the following that recreates the issue:
where onKlick is onClick. When I remove the 'method="post"' from the form tag, the problem disappears. However, the page then randomly fails to submit.
Who knew that furniture could be so violent? Put this tiny ad out there to see what happens: