so just write your own validation messages.
If you use JSF 1.2, you can provide the 'label' attribute for the inputText. In this case, the label will be shown instead of component id.
See example source code at http://livedemo.exadel.com/richfaces-demo/richfaces/messages.jsf
If you would like to remove the prefix of the message in general, the custom validation message, suggested by Ilya, will work for you.
thank you. setting label was the right thing for me.