For a continuous scale variable, any observation that cannot be interpreted as a number will be treated as missing. Blank cells, cells containing text, or cells containing anything that isn't a number will be treated as missing observations.
For clarity we recommend using a dash to indicate a missing value, or enter a textual description to document why the value is missing. Excel's cell Notes/Comments can also be used to attach pop-up comments to document cells containing missing observations.
BEWARE If blank cells are used to indicate missing be aware that an entire row of missing observations will cause Analyse-it to believe it has found the blank row indicating the end of a dataset. If this happens use a dash to indicate missing, then Analyse-it will correctly identify the extent of the dataset.
When importing or copy-pasting data from another application missing values will usually be imported as a dash or as a blank cell. Older statistical software packages often use a special value (usually very large) to indicate missing, which can be replaced with a dash or blank cell using Excel's Find & Replace feature.