User Annotations in Ajax
http://www-128.ibm.com/developerworks/edu/wa-ajaxannot-i.html
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Travis, Greg
IBM
2006

Abstract:

The ability to add notes and comments to your Web site can be a powerful and attractive feature for users. This tutorial demonstrates how to implement an Asynchronous JavaScript and XML (AJAX)-based user annotation system in the form of yellow sticky notes that sit on top of regular Web page content. The only additional, required configuration is a back-end Perl script that stores the annotations.