Finally, I found this Facebook modal styling, which looks just like real one. It looks to be a part of David Walsh's LightFace lightbox, which is based on MooTools. It'll look on your Facebook apps or blogs.
Below is mark-up of this modal:
<div class="popup" >
<div class="content" >
<h1 class="fb">Like this on Facebook</h1>
<p>Still a better story than Twilight!</p>
<div style="height: 80px;"></div>
<a href="#" class="close">Close</a>