Highlight Errors
Property of the ScriptLine : Pre-Processing.
In the Unicode version of Q++ Studio, this property is one of the options of the Generation Options property.
When this property is set to true, Q++ will highlight (in yellow), any textbox where it encounters a token error (token not found, translation not found, …). This is useful if the person proofing the output file does not have Q++, since the errors "jump out" visually.

However if the proofer has Q++, it much easier to use the feature Viewing the Errors in QuarkXPress. You can set the default value of this property using the TOOLS|preferences.