Secure pages need to use all secure elements for the design of the page to show correctly.  You can paste the link that is not working onto this site http://www.whynopadlock.com, and it will show all the insecure items that could be causing issues with the style of your page.  Also, if you are using absolute (full) URLs for the unsecure content on your secure page, you should use relative links instead.  Relative links are accessed inside of the secure page. See Relative URLs versus Absolute URLs for more information about the differences. Alternately, if you are using Mozilla Firefox or Google Chrome, you can press F12 to use the Firefox or Chrome console feature. This will also show all insecure items.

If you are getting this error, disable the WYSIWYG (little pencil icon with a prohibitory sign over it in the top right corner of the WYSIWYG), and go through the code looking for images or scripts with "http://". Once you have found the problem URL, replace "http://www.yourdomain.org" with a "..".

For example, use the following code: <img src "../images/picture.gif">
Instead of this code: <img src "http://www.yourdomain.org/images/picture.gif">

Another example: use the following code: <script type="text/javascript" src="../js/script.js"></script>
Instead of this code: <script type="text/javascript" src="http://www.yourdomain.org/js/script.js"></script> 

Two other things to keep in mind that can also cause this error:
  1. A reference to an asset that does not exist, e.g. image, Flash object, stylesheet, Javascript, etc. Since Luminate Online's page_not_found page is by default non-secure, an HTTP request to a non-existent file will result in a browser security warning.
  2. If there is an object tag on the page, e.g. a Flash object, the codebase attribute must be secure.
So use this code (with https):
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="https://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=9,0,28,0"> 

Instead of this code (with http): 
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=9,0,28,0">

*One thing to note when some of the components are insecure this will prevent an Owner or Verified by when viewed in Firefox.