jQuery UI has some nice convenient CSS styles for alerting and highlighting. I can see it at the themeroller site -- look on the right hand side. Is there a Javascript interface
Apply the appropriate CSS classes for the desired interaction cue from the UI/Theming/API page: .ui-state-highlight for highlight and .ui-state-error for error. You can do it statically or use .addClass('ui-state-highlight') or .addClass('ui-state-error') to do it dynamically.