#a {
    position: relative;
}

#a div {
    display: block;
    color: red;
    width: 200px;
    height: 200px;
    background-color: #FF0;
    position: absolute;
    top: 10px;
    left: 10px;
    cursor: default;
	z-index:1;
}

#a:hover div {
    display: block;
}