Spanish people don´t like talking about how much they earn, so talking about your salary is not considered in good taste. It is also in good taste to speak about details of your intimate relationships, the cost of your personal purchases or racist statements
One thing that is considered rude behavior that might be normal in certain other cultures is proselytism. Especially at work. I refer to people constantly trying to convince others of their political and religious views at times and in places not meant for this.