Jan-When I first woke up this morning I had an inspiration as to how to at least stop some stupid spammers from hijacking the page. This won't work if they have Javascript disabled in their browser, but it would probably foil some people from attempting to use the page in the manner you describe. I created some head tags in the tellafriend.php file (because I think it needs head tags to work), put my css link in there, and also added the Javascript in the attached files (sorry, I've got this crazy keyboard that doesn't let me type pointy brackets at all so it is easiest for me to provide it to you in an attached text file).
The "http://www.mysite.com/mod/resource/view.php?id=75" in the attached file is the path to the frames page that includes the tellafriend.php. Once I uploaded this, I tried accessing my page as you did, and it simply loaded the whole frames page, without the automatically filled in values.
General plugins
Moodle Tell a Friend Script
This discussion has been locked so you can no longer reply to it.