When one of your functions raises an exception dajaxice returns as response the DAJAXICE_EXCEPTION message. On every response dajaxice.core.js checks if that response was an error or not and shows the user a default error message Something goes wrong.
This behaviour is configurable using the new Dajaxice.setup function.
Dajaxice.setup({'default_exception_callback': function(){ alert('Error!'); }});
In this new version you can also specify an error callback per dajaxice call.
function custom_error(){
alert('Custom error of my_function.');
}
Dajaxice.simple.my_function(callback, {'user': 'tom'}, {'error_callback': custom_error});