// displayOverlay displays a slightly transparent overlay on top of the content.
function displayOverlay() {
	var fade = document.createElement("div");
    fade.id = "overlay";
    document.body.appendChild(fade);
    }
    
    
// displayDialog displays a dialog box on top of the content.
function displayDialog(w, h) {
     var wrapper = document.createElement("div");
     wrapper.id = "wrapper";
     document.body.appendChild(wrapper);
	
	var dialog = document.createElement("div");
	dialog.id = "dialog";
	wrapper.appendChild(dialog);
	var dialogCss = {
		"margin-left" : (w/2)*-1 + "px", // width/2
          "top"         : (h/2)*-1 + "px", // height/2
		"height"      : h + "px",
		"width"       : w + "px"
		};
	$("div#dialog").css(dialogCss);
}