I wrote a little script to count banner clicks to the db (MySQL). It does this via $_GET['parX'] variables from click.php?par1=10&par2=20&par3=qqq
And i'm often getting database entries having correct two first parameters and empty third one. These clicks are often numerous (10-20 in a row), so i assume they may be from some bots masking for humans, but there are some that are only 1-2 in a row and they can be from real people.
How this can be that the third parameter from $_GET becomes empty?