Firefox 6 and scratchpad

Trying to use the Scratchpad in FireFox 6 I come up with problems.

If I enter

Code:

alert ( "test ");

and select the 'Run' option the alert box appears on screen with no problem.


If, however, I enter

Code:

document.write( "test ");

I get a 'Security error undefined' message.

Obviously I am missing something very obvious but for the life of me I cannot fathom it out.