HTML attribute "hasbox"

I'm trying to solve some rendering issues in IE9 and have come across an tag attribute I'm unfamiliar with - hasbox.

It looks like IE is injecting the attribute at runtime (it's not in my sources). I've searched numerous sites, including stackoverflow, without finding anything useful... the search engines (Google, Bing, Yahoo) return plenty of exampl开发者_开发问答es showing html tags with the attribute hasbox="2" but otherwise the results are irrelevant.

Can anyone explain this attribute, or point me to a resource where I can learn more?

TIA

Are you using a javascript called boxover.js? See http://www.codingforums.com/showthread.php?t=150218 and http://web.archive.org/web/20090526084653/http://boxover.swazz.org/

http://www.webmasterworld.com/html/4013481.htm

This is the only thing I can find about it that isn't being used in an example.

Do you have anything like that installed that could be doing it?