If you see that not all browsers are recording, or suspect that not all your traffic is being recorded, this may be due to a (hard) break in the script.
For example, if the beginning of your script looks like this:
the (hard) break after the word "defer" may prevent some browsers from picking the visit? up. Firefox, for example, will read the script correctly, while Safari and Internet Exporer may not.
the correcttion looks like this:
for more details, see this posting: