Customize default portlet error messages

Hello,

I received a question to "customize" the error messages displayed by default when a portlet is not available,…

By "customize", I mean internationalization and modification of the style (colors, font size,…)

The error messages the customer would like to customize are :

• Portlet Displays a Portlet Consumer Error
• Portlet Displays a Portlet Timeout
• Portlet Displays a Remote Portlet Communication Error
• Portlet Displays a Remote Portlet Error
• Portlet Displays a Server Connection Failed Dialog

Do you know how these messages can be changed, to use a resource bundle, and how I can change the style ?

I've seen that the error messages were displayed with the class "xq", but I don't know if this class is specific to these messages or if I will have a side effect by modifying it.