Thank you both! I totally agree with you, but as soon as I restrict referer checking to the image.php script only, there is a flaw appearing: image.php then gets downloaded by the browser instead of displaying it. Do you have any idea why this happens? It would be great if I could restrict the check only to this one .php file, but - as said - it does not work here...

Thank you again for your kind help and support,
Amitz