<form id="form" style="background: green; width: 200px;">
<input type="button" onclick="return false;" value="login">
<div style="display: none; height: 50px;">
<input id="inp" name="inp" >
</div>
</form>
<script>
window.onload = function () {
var form = document.getElementById('form');
var div = form.children[1];
var coords, x, y;
form.onmouseover = function () {
div.style.display = 'block';
document.onmousemove = function (e) {
coords = form.getBoundingClientRect();
x = e.clientX;
y = e.clientY;
if (x > coords.right || y > coords.bottom || x < coords.left || y < coords.top) {
div.style.display = 'none';
document.onmousemove = null;
}
}
}
}
</script>
