Rails spinoffs - Nov 2006 - what is _extended="true" in explorer

On a function, I collect the innerHTML of an element and in explore I can
see a tag that i haven''t write on my html. The tag is
_extended="true" and
it''s broking my script when I make element.update with the code I
obtain.
Somebody can explain me what is this tag and where I can get information
about it?

Thanks
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