One of Excel's background error checks (Formulas > Error Checking), by the name the file
stores it under, or one of SheetXL's own. A cell can be told to ignore a check
(ICellRange.setErrorIgnored); Excel then draws no error indicator on it for that rule.
Remarks
The checks SheetXL runs fire through ICell.getAnomalies and the anomalies feature;
an ignored check does not fire. Ignores follow their cells through inserts and deletes, are
never copied, and leave a cell that is written or cleared, as in Excel.
One of Excel's background error checks (Formulas > Error Checking), by the name the file stores it under, or one of SheetXL's own. A cell can be told to ignore a check (ICellRange.setErrorIgnored); Excel then draws no error indicator on it for that rule.