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I've mailed google many times to correct this spell error ( which IMHO it is ) but maybe they thought I'm just a naughty guy :).
Well, here it is. Under Googles -Webmaster Info there is a para called Multiple indices, (http://www.google.com/webmasters/2.html#B1) here, the spelling of cannot is spelled as can not.
If you feel it's incorrect, do pass on this message. If I'm right, I deserve a 1 up increase in my PR na? Just Kidding :P