[mycrashedmind]

попроще и с jquery

var mouse_event = 0
				var differenceX = 0
				var differenceY = 0
				$('#dialog_title').mousedown(function(e){
					differenceX = e.pageX-parseInt($('#dialog').css('left'))
					differenceY = e.pageY-parseInt($('#dialog').css('top'))
					mouse_event=1
				})
				document.onmouseup = function(){
					mouse_event = 0
				}
				document.onmousemove = function(e){
					if (mouse_event == 1){
						$('#dialog').css('left',e.pageX-differenceX)
						$('#dialog').css('top',e.pageY-differenceY)
					}
				}

<div id="dialog">
<div id="dialog_title">Title<spa id="dialog_close" style="position:absolute;right:5px;top:3px;cursor: hand;"></span></div>
<div id="dialog_content"></div>
</div>