Google Analytics was missing the functionality to measure the Ajax Pages which
are generated asynchronously using javascript. This limitation was
finally removed in 2011 when the Google Analytics Tracking Code
themselves became asynchronous. Today you will not find the old code.
For monitoring the Ajax Pages you need to modify the Google Analytics Tracking Code.
For Example if you have a page say "original.php" which is generally
loaded, viewed directly by any user and an Ajax Page say "ajax.php"
which is loaded asynchronously in the "original.php" then the Google
Analytics Code will be in "original.php" and "ajax.php" will not have
any Tracking Code.