Problems using colorbox to load an external non ssl hyperlink from an ssl website

Problems using colorbox to load an external non ssl hyperlink from an ssl website

As above, I run a website that uses ssl encryption (https) and would like to open an external non-ssl hyperlink (http) to a pdf using the colorbox plugin.

I do this using the following code, however nothing seems to be loading, any ideas?
  1. <script>
  2.       jQuery(window).load(function() {
  3.             jQuery("a.linkColorbox").colorbox({iframe:true, fixed:true, width:"75%", height:"75%"});
  4.       });
  5. </script>
  6. <a title="" target="_blank" href="http://www.somewebsite.com/Equipment.pdf" class="linkColorbox cboxElement">