xhprof is a PHP profiler. It will tell you why your pages are slow.
To use it with your sites, add this to .htaccess in the root folder:
php_value auto_prepend_file /home/steve/public_html/xhprof_lib/header.php php_value auto_append_file /home/steve/public_html/xhprof_lib/footer.php
After doing this, you will see a link at the bottom of each page that says “Profiler Output”. Have fun!