Make a Javascript Pop-up That Doesn't Get Blocked and Show it Only Once

I'm honest to say that I am not an expert with client-side scripting, especially Javascript. But I needed a way to show a pop up to a visitor when he visits the site, and only show it once per day. I immediately debunked the idea of using window.open method because it will be 90% sure that pop-up blockers will instantly stop the new window when initiated. I thought of using the Lightbox technique for it, but lightbox was too limited with images, so I googled around for an alternative which can show HTML, then came Thickbox.