function addToList() {
	if(textbox.value != ''){
		var list = document.getElementById('list');
		item = document.createElement('li');
		item.innerHTML = '<input type= "checkbox" onClick = "removeFromList()"/>'+textbox.value;
		list.appendChild(item);
		document.getElementById("textbox").value= "";
	}
}

function removeFromList() {
	var list = document.getElementById('list'),
		items = Array.prototype.slice.call(list.childNodes),
		item;
	while (item = items.pop()) {
		if (item.firstChild && item.firstChild.checked) {
			var text = list.firstChild.innerText;
			alert(text);
			list.removeChild(item);
		}
	}
}

function addToList() {
	if(textbox.value != ''){
		var list = document.getElementById('list');
		item = document.createElement('li');
		item.innerHTML = '<input type= "checkbox" onClick = "removeFromList()"/>'+textbox.value;
		list.appendChild(item);
		document.getElementById("textbox").value= "";
	}
}

function removeFromList() {
	var list = document.getElementById('list'), items = Array.prototype.slice.call(list.childNodes), item;
	while (item = items.pop()) {
		if (item.firstChild && item.firstChild.checked) {
			var text = list.firstChild.innerText;
			var completedList = document.getElementById('completed');
			completedItem = document.createElement('li');
			item.innerHTML = '<input type= "checkbox" onClick = "addBack()" checked/>'+text;
			list.removeChild(item);
			completedList.appendChild(item);
		}
	}
}

function addBack() {
	var list = document.getElementById('completed'), items = Array.prototype.slice.call(list.childNodes), item;
	while (item = items.pop()) {
		if (item.firstChild && item.firstChild.checked == 0) {
			var text = list.firstChild.innerText;
			var completedList = document.getElementById('list');
			completedItem = document.createElement('li');
			item.innerHTML = '<input type= "checkbox" onClick = "removeFromList()" value = "0"/>'+text;
			list.removeChild(item);
			completedList.appendChild(item);
		}
	}
}

Update Checking and Checkbox Behavior
Update Checking and Checkbox Behavior

Remove multiline statement broke by commas. Make it all one line.
When the item is checked, move it to completed.
If the object is checked when in completed, move it back to the active
list.
