Вопросы по - Диалоговое окно - Вопросы по CSS

.modalDialog {
	position: fixed;
	top: 0;
	right: 0;
	bottom: 0;
	left: 0;
	background: rgba(0,0,0,0.8);
	z-index: 99990;
	opacity: 0;
	-webkit-transition: opacity 400ms ease-in;
	transition: opacity 400ms ease-in;
	pointer-events: none;   	
}
#dral {
    resize: both;
	overflow: hidden;
	position: absolute;
    left: 0;
    top: 0;    
	
	min-width: 320px;
	min-height: 240px;
	max-width: 640px;
	max-height: 480px;
}
.modalDialog:target {
	opacity: 1;
	pointer-events: auto;
}

function drag_start(event) {
    var style = window.getComputedStyle(event.target, null);
    event.dataTransfer.setData("text/html",
    (parseInt(style.getPropertyValue("left"),10) - event.clientX) + ',' + (parseInt(style.getPropertyValue("top"),10) - event.clientY));
} 
function drag_over(event) { 
    event.preventDefault(); 
	
    return false; 
} 
function drop(event) { 
	event.stopPropagation();
    var offset = event.dataTransfer.getData("text/html").split(',');
    var dm = document.getElementById('dral');
	
    dm.style.left = (event.clientX + parseInt(offset[0],10)) + 'px';
    dm.style.top = (event.clientY + parseInt(offset[1],10)) + 'px';
    
	event.preventDefault();
	
    return false;
} 
var dm = document.getElementById('dral'); 
dm.addEventListener('dragstart',drag_start,false); 
document.body.addEventListener('dragover',drag_over,false); 
document.body.addEventListener('drop',drop,false);