A friend shared a webpage which was supposed to render a Tableau visualization. However, when I opened that URL in my Firefox browser, I got an empty page.
At first, I suspected that one of my many Firefox extensions was blocking the Tableau visualization. I disabled all extensions and the webpage was still empty.
I decided to check out the HTML source of the webpage by right-clicking on the page and choosing View Page Source. I saw that the HTML was pretty simple. The main suspect seemed to be a script tag that was pulling in a Javascript file from http://tableaureporting.foobar.com/javascripts/api/viz_v1.js.
So I suspected that Firefox was not loading this Javascript file for some reason. Why might that be?
Time to break out the Developer Tools in Firefox by pressing F12. The Console tab showed an error: it had blocked the script due to something called mixed content use. Thankfully, the error message was linked to a Mixed Content page that explained why: I was looking at a HTTPS webpage that was trying to load a Javascript file (active content) from a HTTP URL. To protect me, it was blocking this active content.
So Firefox is protecting me. That’s good, but I knew the URL from my friend is safe and I wanted to really see that visualization.
Might there be a security setting that I could disable? Turns out there is. Head over to about:config in Firefox and toggle the security.mixed_content.block_active_content setting from default to false.
Voila, I could see my Tableau visualization after this!
Tried with: Firefox 68 and Ubuntu 18.04