Ever wonder exactly what changes have been made to the running config? Should you save them before reloading or would that break everything. Use show archive config differences nvram:startup-config system:running-config to view the difference between the startup config and the current running config.

show archive config differences nvram:startup-config system:running-config

router#show archive config differences nvram:startup-config system:running-config
Contextual Config Diffs:
+ip access-list extended test

120651-149720#

More Info:
http://www.2000trainers.com/cisco-ccna-07/ccna-router-configuration-files/
http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gt_diff.html
http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gt_diff.html#wp1068464