What do you see, if anything -- do you get a blank area where the iframe should be?

If you check the browser console (formerly known as the error console), do you see any errors referring to problems with the framed document? You can open the console by pressing Ctrl+Shift+j, and you can click the CSS button to show or suppress style warnings so you can find the actual errors more easily.

Also, if you see a "shield" icon in the address bar to the left of the URL, it's this: Firefox 23 introduced a new security feature which will block iframes with an HTTP address from displaying in an HTTPS page. This "mixed content blocking" is described in more detail in this article: Mixed content blocking in Firefox

I think you are right. Attached is the screen capture of the blocked mixed content. do you know how I can fix this?

Hi winters_c, is it an option to make all of your content either secure or insecure, and not mix them? Otherwise, users will need to use the "shield" icon to allow it every time they visit the page.

I found the anwser. You guided me correctly... Thank you!

what about the Google Chrome browser? How do I enable the mixed content to be displayed?

Hi winters_c, you wrote:

what about the Google Chrome browser? How do I enable the mixed content to be displayed?

That I do not know, but you might find the answer by searching Google's forum for Chrome: https://productforums.google.com/forum/#!forum/chrome