The browser that is used to access the web site is contained within the log file in field 12. It may be interesting to display the list of browsers used to access your site. The following code will assist you in displaying the list of accesses by the reported browser:

{ browser[$12]++ }
END {
    for ( b in browser )
        print b, " has accessed ", browser[b], " times."
    }

You can see how we can create little plugins to awk with these files and adjust the field and array names to suit your own liking. The output is shown in the following screenshot:

Interestingly, we see that the Mozilla 4 and 5 make up the majority of the requesting client. We see that Mozilla 4 is listed here 1713 times. The Mozilla/5.0 entry here is malformed with an extra double-quote. It appears later with 27K accesses.