Usability of XmlHttpRequest
•Already discussed "forgiveness" and browser support, some other points ...
–1.  Know the difference between a web application and a website
•Web applications - Richer, use AJAX, use XmlHttpRequest, comply to UI guidelines
•Web sites - collection of pages, do not need extra richness, comply to web site guidelines
•When you mix these - you confuse the user
•User expectations - what do they expect to see?
•Accessibility - needs to be true for both