In StackEdit v4 I can make the preview show fancy things like:
using this markup:
<div class="alert alert-success"><i class="icon-ok"></i> **SUCCESS:** Markdown formatting _is_ supported here.
</div>
<div class="alert alert-info"><i class="icon-lightbulb"></i><strong>INFO:</strong> Markdown formatting _is_ supported here.
</div>
<div class="alert alert-warning"><i class="icon-right-hand"></i> **WARNING:** Markdown formatting _is_ supported here.
</div>
<div class="alert alert-danger"></i><i class="icon-attention-alt"></i>**DANGER:** Markdown formatting _is_ supported here.
</div>
> <i class="icon-quote-left"></i> The secret to creativity is knowing how to hide your sources.
> -- <cite>[Albert Einstein][1]</cite>
[1]:http://www.quotedb.com/quotes/2112
How can I add customizations to the StackEdit v5 Preview pane to handle icon fonts and custom CSS?