Are you having problems seeing some of you content in Desire2Learn? Firefox version 23, which was just released, introduced “mixed content” blocking for the first time in the Firefox browsers. Chrome did this a year ago. You can tell the browser to show you the content in both browsers (see video examples below).
There are, however, some differences between the two. The biggest difference is that Chrome will remember you approved the site for the whole time you are at the site. Firefox, on the other hand, will request approval for each page you access on the site.