Moin
<form action="phpfile.php" METHOD="POST" onsubmit="javascript:screenshot('','Screenshot','width=600,height=450')">;
da vermisse ich auch das target="Screenshot"
so solte es eher klappen:
<form action="phpfile.php" METHOD="POST" onsubmit="screenshot('','Screenshot','width=600,height=450');return true" target='Screenshot'>;
Gruß
rfb