Found this while googling. I needed a way to prevent users from backing up and sending dual requests. This is what I found.
Use the history.forward() JavaScript directive in the head section of each page. Thus, when the user attempts to back up within your site, the script will bounce him forward each time.
Include the following text in the <head> portion of each page.
<script>
history.forward();
</script>
The user can always leave by manually entering a new URL in the address bar. The first time you visit this page, you will be able to use the back button to return to the previous site you visited. The back button is effectively disabled and users are forced to use the provided breadcrumbs.
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