The type selector ” was not processed, because the type was not used in the application.

The type selector ‘Alert’ was not processed, because the type was not used in the application.

Reason
The compiler is telling you that it can’t find a case where the CSS that you are including inline or in a stylesheet is being used in the application. This is regardless if it will be used at another time. If it’s not being used in the application it’s not included at run time.

To remove this warning add the following line to the command line arguments:

-show-unused-type-selector-warnings=false

Note that “unused’ type selectors aren’t included to keep the file size down.

If you want to include every CSS type selector whether it’s being used or not add the following line to the command line arguments:

-keep-all-type-selectors=true

To change command line arguments in Flash Builder navigate to Properties > Flex Compiler > Additional Compiler Arguments.