stem, так?
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title></title>
<!--<script src="http://code.jquery.com/jquery-latest.js"></script>-->
<style>
#oneclickbox {
background: orange;
padding: 50px;
width: 30%;
}
.oneclickorder-productview {
background: red;
}
</style>
<body>
<a id="linkoneclickorder" class="link-oneclicorder" href="">Купить в 1 клик</a>
<div id="oneclickbox" style="display:none;" class="oneclickorder-productview-container">
<button>Закрыть</button>
<div class="oneclickorder-productview">
<form action="">
<input type="text" /><br />
<input type="text" /><br />
<input type="submit" />
</form>
</div>
</div>
<script>
var open = document.getElementById('linkoneclickorder'),
close = document.querySelector('#oneclickbox > button'),
oneclickbox = document.getElementById('oneclickbox');
open.onclick = function() {
!(oneclickbox.offsetHeight) && (oneclickbox.style.display = 'block');
return false;
};
close.onclick = function() {
oneclickbox.style.display = (oneclickbox.offsetHeight) ? 'none' : 'block';
};
</script>
</body>
</html>