We used to go to some elaborate trouble to allow you to use
target="_blank" on anchor links within our sandboxed iframe. We're not sure if it was a behavior change in browsers or if it was something we changed over time regarding sandboxing or other security measure, but now,
target="_blank" links work as expected in previews: they open links in a new window/tab.
<div <script> var yep = "you'll see this."; </script>