Debug your plugins and themes.
kb_debug.php and 'kb-debug.css' to the
/wp-content/mu-plugins/ directory. (Create this directory if it doesn't exist).
NOTE: These files must be placed directly under mu-plugins: ie mu-plugins/kb_debug.php and mu-plugins/kb-debug.css.
Putting these into mu-plugins allows the plugin to capture the most number of hooks it can.