Failed to load widgets

i don't understand anything.
i was doing the tutorial and all was going perfect.
in the middke of the stept 5
But now i can see anything in the browser except the mesage 
Failed to load widgetset

¿Why does this error occurr?

Upss,
Now i did mvn wildfly:deploy in a console and now works...
i don't understand anything
What has it happened with th e widgetset...
 

Now again appear the error failed to load widgetset,

It is so bizarre,

To sove it.
I have to do mvn clean.