Weird window in Firefox/Safari

[idkew]

Sometimes when I am running Firefox (and I think Safari) I get this hidden window. It is not found in the window menu. It is not selectable when I am in expose, when I click on it, it does not appear, but i am sent to Firefox (or safari). The only way I know it is there is when i am expose'ing. It is always the same size and in the same place on the screen.

What do you think it is?

I have attached a shot of it during expose and did a bad job of highlighting it.

 

[Logik]

this is a known issue with firefox.. (not safari) it's a window that is left open so that when you close all windows firefox stays running. if that window closes then firefox closes. it's a known bug between firefox and expose... do a search on here ... there is currently no work around and has been submitted to bugzilla for firefox..