Based on the apache path, it looks like you installed Apache httpd
from source (or via a cpanel-compiled source installation), as opposed
to using the httpd package for your system (are you on centos?).
Since your installation of Apache httpd is not from the system's
package manager, the mod_pagespeed RPM package won't work for your
system without some work. It will install mod_pagespeed into the wrong
location. So the warning you are getting is perhaps not giving you all
the information it could, but it's helping to prevent you from
installing mod_pagespeed on your system where it wouldn't otherwise
work. We will update our docs to make this clearer.
When you have an Apache httpd install that isn't package-managed, the
easiest way to install mod_pagespeed is to compile it yourself from
source.
There are instructions on how to do that here:
http://code.google.com/p/modpagespeed/wiki/HowToBuild
Once you have it compiled, you can try to use the install_apxs.sh
script to actually install the module on your system. install_apxs.sh
is also documented in the HowToBuild wiki page.
Please let us know if you encounter any issues building or installing. Thanks!