The spelling and grammar checker works on a per-document/per-session basis. Basically when you run the checker, if you leave some items uncorrected and close the document, it will prompt for those same items the next time you open the document and run the checker.

Ignore rule basically ignores all grammar items that fail that particular grammar rule. For example, if the grammar checker stops on a fragment sentence and you select Ignore Rule, it will not stop on any other fragment sentences in the rest of the document.

Hope this helps.

-SW