In IE it is giving me the "some items on the page are not secure" message. I have tracked it down to this line:
which is a lightbox script I downloaded. I tried making the src relative or absolute with https it happens either way. And only in IE.
Heres the page if you need to see it: Clicky
Looking at your page in Fiddler, I see a request to https://www.kranichs.com/images/bottombax_02.jpg, which is a 404.
IE considers the 404 error message as unsafe content, so if you are including that (in an IFRAME or something) then you will see the mixed content error. Fix that and see what happens.
If nothing changes when that file exists, and you don't see any HTTP requests in Fiddler, it's possibly the removeChild problem - if you remove a DIV with a background image (as a lightbox might) then you will see the mixed content error.