var browser = new Browser();
// Global object to hold drag information.
var dragObj = new Object();
dragObj.zIndex = 0;
//-----------------------------
// Determine browser and version.
function Browser() {
	var ua, s, i;
	this.isIE    = false;
	this.isNS    = false;
	this.version = null;
	ua = navigator.userAgent;
	s = "MSIE";
	if ((i = ua.indexOf(s)) >= 0) {
		this.isIE = true;
		this.version = parseFloat(ua.substr(i + s.length));
		return;
	}
	s = "Netscape6/";
	if ((i = ua.indexOf(s)) >= 0) {
		this.isNS = true;
		this.version = parseFloat(ua.substr(i + s.length));
		return;
	}
	// Treat any other "Gecko" browser as NS 6.1.
	s = "Gecko";
	if ((i = ua.indexOf(s)) >= 0) {
		this.isNS = true;
		this.version = 6.1;
		return;
	}
}
//-----------------------------
function dragStart(event, id) {
	var el;
	var x, y;
	// If an element id was given, find it. Otherwise use the element being clicked on.
	if (id)
		dragObj.elNode = document.getElementById(id);
	else {
		if (browser.isIE) dragObj.elNode = window.event.srcElement;
		if (browser.isNS) dragObj.elNode = event.target;
		// If this is a text node, use its parent element.
		if (dragObj.elNode.nodeType == 3) dragObj.elNode = dragObj.elNode.parentNode;
	}
	// Get cursor position with respect to the page.
	if (browser.isIE) {
		x = window.event.clientX + document.documentElement.scrollLeft + document.body.scrollLeft;
		y = window.event.clientY + document.documentElement.scrollTop + document.body.scrollTop;
	}
	if (browser.isNS) {
		x = event.clientX + window.scrollX;
		y = event.clientY + window.scrollY;
	}
	// Save starting positions of cursor and element.
	dragObj.cursorStartX = x;
	dragObj.cursorStartY = y;
	dragObj.elStartLeft  = parseInt(dragObj.elNode.style.left, 10);
	dragObj.elStartTop   = parseInt(dragObj.elNode.style.top,  10);

	if (isNaN(dragObj.elStartLeft)) dragObj.elStartLeft = 0;
	if (isNaN(dragObj.elStartTop))  dragObj.elStartTop  = 0;

	// Update element's z-index.
	dragObj.elNode.style.zIndex = ++dragObj.zIndex;

	// Capture mousemove and mouseup events on the page.
	if (browser.isIE) {
		document.attachEvent("onmousemove", dragGo);
		document.attachEvent("onmouseup",   dragStop);
		window.event.cancelBubble = true;
		window.event.returnValue = false;
	}
	if (browser.isNS) {
		document.addEventListener("mousemove", dragGo,   true);
		document.addEventListener("mouseup",   dragStop, true);
		event.preventDefault();
	}
}
//-----------------------------
function dragGo(event) {
	var x, y;
	// Get cursor position with respect to the page.
	if (browser.isIE) {
		x = window.event.clientX + document.documentElement.scrollLeft + document.body.scrollLeft;
		y = window.event.clientY + document.documentElement.scrollTop + document.body.scrollTop;
	}
	if (browser.isNS) {
		x = event.clientX + window.scrollX;
		y = event.clientY + window.scrollY;
	}
	// Move drag element by the same amount the cursor has moved.
	dragObj.elNode.style.left = (dragObj.elStartLeft + x - dragObj.cursorStartX) + "px";
	dragObj.elNode.style.top  = (dragObj.elStartTop  + y - dragObj.cursorStartY) + "px";
	if (browser.isIE) {
		window.event.cancelBubble = true;
		window.event.returnValue = false;
	}
	if (browser.isNS) event.preventDefault(); 
}
//-----------------------------
function dragStop(event) {
	// Stop capturing mousemove and mouseup events.
	if (browser.isIE) {
		document.detachEvent("onmousemove", dragGo);
		document.detachEvent("onmouseup",   dragStop);
	}
	if (browser.isNS) {
		document.removeEventListener("mousemove", dragGo,   true);
		document.removeEventListener("mouseup",   dragStop, true);
	}
}
//-----------------------------