Flash Detection Scripts

I implemented the Flash Detection script that I found here @ Kirupa.com and after testing, thought everything was working correctly. Today I found out that someone using a Mac wasn’t able to see the GIF that should come up asking for the user to go to Macromedia.com to load the flash player but rather a miniture version of the swf that was created for the site. Does anyone know what steps I need to take to make the detection script viable for both environments. Thanks, S.