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The w3c’s attempt to standardize the de facto XHR standard.
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Docs on the Mozilla implementation of XHR
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Discussion of some of the issues of authenticating REST-style web services including an example of securing your services with Basic or Digest auth using Apache HTTP Server.
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What I Didn’t Know About XHR – O’Reilly XML Blog
Interesting test case explaining browsers’ default limitations on number of concurrent XHR requests.
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Bug 339530 – Basic auth fails with XMLHttpRequest
A bug related to supporting the user and password arguments to XmlHttpRequest#open
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MSDN XMLHttpRequest#open method
Microsoft’s documentation on IE’s API for the XmlHttpRequest’s open method. It also talks about IE’s overly-aggressive GET caching.
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XMLHttpRequest HTTP Feature Tests
Executable test case to determine your current browser’s support for XHR features.
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Executable test case to determine the correctness of your browser’s resource caching via XHR.
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Using Basic Authentication via with AJAX to access CMP
Solutions for using Basic Auth from an Ajax application sans ugly browser dialog.
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Additional commentary and analysis on the ‘Using Basic Authentication via with AJAX to access CMP‘ wiki page