Forensic Challenge 2010/5 - Log Mysteries - What Apache version was used?

Carl Pulley, a loyal follower of our Forensic Challenges, has written up an analysis on how could one determine the Apache version that generated the logs. His analysis can be found at http://acme-labs.org.uk/news/2011/01/20/apache2-version-analysis/ and http://acme-labs.org.uk/news/2011/01/21/apache2-version-analysis-data-visualisation/. Check it out!