how to detect when a shortcut key is pressed in javascript

How can i detect a shortcut key, [ in my case [ ctrl + shift + k ] ] in javascript? Like, i have to show a dialog if user presses this key.

Answer

document.onkeydown = keydown;

function keydown(evt){
  if (!evt) evt = event;
  if (evt.ctrlKey && evt.altKey && evt.keyCode==115){ //CTRL+ALT+F4
    alert("CTRL+ALT+F4"); 
  }
  else if (evt.shiftKey && evt.keyCode == 9){ //Shif+TAB
    alert("Shift+TAB");
  }
}

Ontop of the url Dominic posted will give you the key codes.