Check this search and click the first results:
google.com/search?q=Gmail+Noti ...
A little sloppy, isn't it?

Looks alright to me, what do you see? What's your first result?

I get taken to toolbar.google.com/gmail-helpe ... which redirects to /notifier_windows.html as I am a Windows user.

no problem found
Can you explain a bit

i've experienced a 404 Not Found now and before several times... i'm on a mac.. strangely enough i do get a favicon (google toolbar)

No abnormal behavior from here