Editing Module:Convert/documentation/conversion data/introduction (section)

=== Should be ===
Some unit codes should not be used—if such a code is used, the template displays an error message telling the editor what unit code should be entered. For example, the code <code>feet</code> should not be used, and that is indicated by entering <code>!''Message''</code> in the Symbol column for the <code>feet</code> entry. There should be no other entries on an error line. The ''Message'' text is displayed as an error if <code>feet</code> is used in a conversion. The text should use the special format codes <code>%{</code> and <code>%}</code> on each side of a unit code. The format codes are replaced with wikitext defined in [[Module:Convert]], and which applies a consistent style to each displayed unit code.