While using Word 2010, I was editing a lengthy manuscript and I erroneously checked "Ignore rule," while editing a grammar error. I wanted to check the "Ignore Once" block so that I can use the rule for most error corrections. How do I get MS WORD 2010 to resume editing and continue employing the grammar rule?

You can do that via File|Options|Proofing>Check Document. Do note that this re-sets all the spelling & grammar checking for the document.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]