challenges facing by the manager of 21st century?

Answer 1

People who want a paycheck but don't want to work.
People you've hired who don't show up for work, or call in.

Answer 2

The key to success (even as a manager) is knowing the right question to ask. Yours is rather broad and thus you will get a wide assortment of answers which you will then need to spend time sorting through in order to find those which suit your needs best. So, consider this as one example of challenges facing the manager in the 21st century: thinking about problems in a critical (analytical, not "bit*hy") way. That said, I might categorize challenges to management/managers in 5-6 buckets:

* globalization of economies: how to design, produce and distribute the right products and services to a culturally diverse market
* diversity: related to the above but worthy of its own class. This is about the fact that many developed economies now rely on increasing numbers of immigrants; that many large companies operate globally and must adapt to markets, customer and employee diversity in tastes, working styles and values.
* always on infrastructure (think Internet) and 24/7 work flows: this increases forces on time to market
* cost containment: this is contributing to outsourcing (another challenge but a subset of this one IMO) as firms focus on their core competencies to manage costs and improve overall competitiveness
* ethics and regulation: business scandals and abuses occur in every country and every country attempts to legislate "proper" business behavior that aligns with its peoples' contemporary social values. It makes for a lot of "bureacracy" in the name of social fairness.