var speed = Math.round(500 / 100);

//change the opacity for different browsers
function changeOpac(opacity, id) {
	var obj = document.getElementById(id).style; 
	obj.opacity = (opacity / 100);
	obj.MozOpacity = (opacity / 100);
	obj.KhtmlOpacity = (opacity / 100);
	obj.filter = "alpha(opacity=" + opacity + ")";
	if (opacity <= 0)
		obj.display = 'none';
	if (opacity >= 100) {
		obj.fadingIn = false;
	}
}

function resetOpac(id) {
	var obj = document.getElementById(id);
	changeOpac(0, id);
	obj.fadingIn = false;
}

function resetOpacs(letter) {
  var noContent = true;
  var arrLetters = new Array("A","B","C","D","E","F","G");
  for (var i= 0; i < arrLetters.length; i++) {
    if (letter != arrLetters[i]) {
      resetOpac('dfs_content_' + arrLetters[i]);
    } else {
      noContent = false;
	}
  }
  
  // if no other content windows are displayed, fade in the default content
  if (noContent) {
    fadeIn("dfs_content_default");
  }
}

function fadeIn(id) {
	var obj = document.getElementById(id);
	clearTimeout(obj.outTimer);
	obj.style.display = 'block';
	if (!obj.fadingIn) {
		obj.fadingIn = true;
		var timer = 0;
		for(i = 1; i <= 100; i++) {
			setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
			timer++;
		}
	}
}

function fadeIn_perm(letter) {
  // make sure that the default content is hidden
  resetOpac("dfs_content_default");	

  // make sure all other content is hidden
  resetOpacs(letter);

  fadeIn("dfs_content_" + letter);
}

function fadeOutEx(id) {
	var obj = document.getElementById(id);
	if (obj.style.opacity != 0) {
		var timer = 0;
		for(i = 100; i >= 0; i--) {
			setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
			timer++;
		}
		obj.fadingIn = false;
	}
}

function fadeOut(id) {
	document.getElementById(id).outTimer = setTimeout("fadeOutEx('" + id + "')", 300);
}