end_opacity = 50; //end opacity, 25 = 25%, 50 = 50%, 100 = 100%, etc.
increase_opacity_by = 10; //how much to increase by each time the timeout ends
timeout = 100; //timeout in miliseconds, 0 = instant fade-out
cur_opacity = 0;
var timer = null;

function initWindow(thewindow,thewindowbackground,thewindowcontent) {
  win = document.getElementById(thewindow);
  winbackground = document.getElementById(thewindowbackground);
  wincontent = document.getElementById(thewindowcontent);
}

function showWindow(thewindow,thewindowbackground,thewindowcontent) {
  initWindow(thewindow,thewindowbackground,thewindowcontent);
	if(timeout > 0) {
		cur_opacity = 0;
	
		winbackground.style.opacity = cur_opacity / 100;
		winbackground.style.filter = "alpha(opacity=" + cur_opacity + ")";
		win.style.display = 'block';
		wincontent.style.display = 'none';
	
		timer = setTimeout("increase_opacity()",timeout);
	}
	else {
		winbackground.style.opacity = end_opacity / 100;
		winbackground.style.filter = "alpha(opacity=" + end_opacity + ")";
		win.style.display = 'block';
		wincontent.style.display = 'block';
	}
}

function increase_opacity() {
	cur_opacity += increase_opacity_by;

	winbackground.style.opacity = cur_opacity / 100;
	winbackground.style.filter = "alpha(opacity=" + cur_opacity + ")";
	
	if(cur_opacity < end_opacity) {
		timer = setTimeout("increase_opacity()",timeout);
	}
	else {
		wincontent.style.display = 'block';
	}
}

function hideWindow() {
	win.style.display = 'none';
}