Computer Tips - Why does Slashdot access a file called "ok.txt" on my site?
Date: 2008jun9
Q. Why does Slashdot access a file called "ok.txt" on my site?
A. It appears they do this when somebody posts anonymously
to see if they are coming from an open proxy.
You can make a file called ok.txt (that contains simply "OK") in your
webserver's root folder to avoid error messages.
More discussion
http://ask.slashdot.org/article.pl?sid=05/06/09/1621232