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The CSS parser now sends parse errors to the JavaScript Console — these include messages such as “Unknown property 'x'. Declaration dropped.”, “Error in parsing value for property 'x'. Declaration dropped.”, and “Expected 'x' but found 'y'. Declaration dropped.”. While these messages are helpful to web developers for diagnosing problems with web page appearance, they tend to clutter the JavaScript Console. This preference allows the parse errors to be disabled.

Possible values and their effects


Report CSS parse errors and display them in the JavaScript Console. (Default)


Suppress CSS parse error messages.


  • Since this feature is not included in Firefox 1.5 (but the parse errors are reported), users may want to use the Console² extension to suppress CSS errors in the JavaScript Console.

First checked in

2005-12-27 by L. David Baron

Has an effect in

  • Mozilla Firefox (all versions since 1.6a — not 1.5.*)

Related bugs

Related preferences