Text widget content not showing up in sidebar

I am trying to put html code for a banner ad in a text widget in the sidebar of my blog (https://www.shearperfection.com/blog). I put the title in (“Anti-Aging”). Then I copy-paste the html code into the body of the widget. I save it, close the widget, and preview the page. Nothing shows up but the title. I do not have an ad blocker running on my computer, and popups are not blocked.

My operating system is Windows 7. My browser is Firefox, and I’ve cleared the cache multiple times and checked the addons and extensions and I’m not finding an ad blocker or popup blocker there either. But it must be a browser issue, because when I check the site in Chrome and Internet Explorer, the banner ad shows up.

How do I fix it so it shows up for people (like me) who use Firefox?