Interesting. Even if single-quotes can be used in html and shouldn't by itself lead to troubles, it's best practice to use whichever is more prevalent in your code for consistency's sake. I'm under the impression double quotes are more commonly used on Roll20 character sheets. Google's HTML Styles Guide recommends using double quotes with HTML, and this seem to be the first case I've seen where it actually seem to have an difference. Edit: I replicated this behaviour