Script Summary: Always show details in the first open message of a gmail conversation. "Details" include the from: reply-to: to: cc: date: subject: mailing list: and mailed-by: headers.
*** In late 2011/early 2012 Gmail changed its appearance, breaking this script. There is no longer a "show details" button at all, only a subtle down-arrow that you can click on to show details, but it covers up other parts of the page. ***
2012: No change to script, but broken.
July 6, 2011: No change to script, and Gmail's Greasemonkey API is fixed!
January 28, 2010: No change to script, but Gmail's Greasemonkey API broke: http://code.google.com/p/gmail-greasemonkey/iss...
March 16, 2009: Added 500ms delay to make the script more reliable (as suggested by http://eric.biven.us/2008/11/25/using-the-gmail...)
March 3, 2009: Updated to work with new Gmail html classes.