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In quite a few content editors, I see code generated that includes attributes of the form


What is this attribute?

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Judging from the sourceIndex Property page on the MSDN and the lack of any mention of sourceIndex at W3.org, I believe it is a proprietary Microsoft tag (and unlikely to be supported - or considered valid X/HTML - by non-Microsoft browsers).

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It is found in a Joomla and Mambo also, so perhaps it is not a proprietary Microsoft tag, unless all the Joomla/Mambo template developers are developing in MS Word. :P – Steve Apr 6 '11 at 2:02
@Steve - Why would the use of proprietary HTML attributes mean that an application was developed with Microsoft software? – danlefree Apr 6 '11 at 2:31
Good question, but what would they need it for? Internet Explorer? – Steve Apr 9 '11 at 11:50
@Steve - Primarily Internet Explorer but, theoretically, any Microsoft .NET application that parses HTML could access the sourceIndex property of an element. If you want to see how the sourceIndex attribute might be used in IE, this article at quirksmode.org includes some examples: quirksmode.org/dom/getElementsByTagNames.html – danlefree Apr 9 '11 at 14:12

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