Script Summary: Mark read tweets using a customizable background color.
Change the value of variable gblBackgroundColorForReadItems, if you don't like the default background color for Marked tweets. Originally part of this script. Now provided as a standalone script.
Update (04/30/09): The script is broken by the new change to Twitter home page which now always redirects the pagination URL to http://twitter.com. Fix the script by using a workaround to figure out whether the lastRead status should be updated or not.
Update (04/03/09): Makes it work with Google Chrome.
Update (03/31/09): Change the Include URLs to http(s)://twitter.com/timeline/home.
Update (09/18/08): Fix the script to work with twitter's new layout
Update (09/18/08): Cover the https twitter pages.