Broken INTERNAL link problem

I keep getting emails from django about broken INTERNAL links which I can't explain:

Referrer: http://www.emetor.com/forum/
Requested URL: /thanks/forum/
User agent: Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)
IP address: xxx.xxx.xxx.xxx

It seems that they are due to a contact form on the referrer page, which after successful submission redirects to http://www.emetor.com/thanks/. When I try a contact submission, everything works just fine. But I'm afraid that I might miss some contact submissions!

Somebody who has an explanation about where the problem could be? Please let me know if you need further information...

The contact 开发者_JAVA百科form does the following:

<form action="/contact/" method="post">

And in the view for contact:

def contact(request):
    if request.method == 'POST': # If the form has been submitted...
        form = ContactForm(request.POST) # A form bound to the POST data
        if form.is_valid(): # All validation rules pass
            ...
            send_mail(subject, message, sender_email, recipients)
            return HttpResponseRedirect('/thanks/') # Redirect after POST
    else:
        form = ContactForm() # An unbound form
    return render_to_response('contact.html', RequestContext(request,{'form': form}))

Log file shows that requested url is "/thanks/forum/", although you mention that successful submission redirect is "/thanks", so check the code where redirect url is created.

Other explanation could be that this link is saved by some crawler or bot and it try to request that page.