   What is difference between ::MessageBox and MessageBox?
  I seen it written in many books differently: in ones - MessageBox(), in others - ::MessageBox(), so what's the difference?   
  With ::MessageBox() you're explicitly stating that you want to call the function in the global namespace. If you just write MessageBox() it will call whatever function with that name in any namespace you currently have access to.   ;  The :: just means use MessageBox() from the global namespace.  This will help get around the fact you might have your own matching MessageBox() function in your own namespace or class.[edit]Dang, beat by 20 seconds :)   ;  Thanks for help :)   